CAN SCIENCE EXPLAIN LIFE? ■*■ By CAKL F. KKAFFT Washington, D. C. Price One Dollar Copyright 1931 by Carl F. Krafft THE SCIENCE PRESS PRINTING COMPANY LANCASTER, PA. FOREWORD The purpose of the present work is to furnish a satisfactory mechanistic explanation for the fundamental life processes, especially in so far as they differ from known physical and chemical processes. The inability of scientists to explain how a complex living organism can reproduce itself through the medium of a single germ cell has caused many of them, even until the present day, to desert the mechanistic school and to return, reluctantly, to vitalistic teachings. Although the author's sympathies have always been with the mechanists, yet after candid and impartial con- sideration of this subject he has come to the conclusion that the arguments of the vitalists cannot be successfully answered on the basis of our previous scientific knowledge, and that the fun- damental life processes have heretofore remained unexplained. Mere analogies do not constitute explanations, nor is the explanation of certain minor details equivalent to an explanation of fundamentals. The spirazine hypothesis was conceived in De- cember, 1925. During the year 1926 every pos- sible effort was made to obtain publication of it in the scientific magazines, but without success. In some cases the article was returned without 4 Can Science Explain Life? any comments whatever, which may have been an expeditious but not a very honorable method of executing the duties which attach themselves to the office of editorship. In those cases where the editors did give it any sort of serious considera- tion it was condemned as being " unscientific " and "contrary to known facts," and was char- acterized as being only one out of many other "equally good guesses,' ' although the author has not yet received from the critics thereof a single suggestion as to what some of those other equally good guesses might be. In still other cases it was returned with certain evasive excuses, as for example that it was "too technical," although the real reason was probably that the author was not sufficiently noted. After the prospects of obtaining publication through the usual channels seemed hopeless, a number of mimeographed pamphlets setting forth the salient features of this hypothesis were prepared and distributed among those who were known to be interested. An abstract notice of them was recorded in Chemical Abstracts, 22, 2584 (July 20, 1928). The present work is a revision of the author's earlier book on "Spirazines," published in the fall of 1930. An effort has been made to clarify some of the explanations, and a considerable amount of new material has been added. CAN SCIENCE EXPLAIN LIFE? INTRODUCTION The various forms of life which are encoun- tered in nature exhibit such a variety of appear- ances and such a profusion of details that the casual observer is often too bewildered by the complexity of his surroundings to gain a clear conception of life processes in their entirety and to distinguish what is fundamental and indis- pensable from what is superficial and unessential. Life is usually recognized by specific bodily form, spontaneous mobility, and responsiveness to stimuli, but these characteristics can all be closely imitated artificially and in the lower forms of life are often entirely absent, so that they must be regarded as secondary characteristics which have developed in the course of evolution and not as primary attributes of life itself. Every living organism is unique in that it con- stitutes an autonomous self-contained entity hav- ing its own specific behavior, and which is capable, under favorable conditions, of growing and pro- ducing others like itself. The phenomena of growth and reproduction are exhibited by every living organism regardless of its rank in the plant or animal kingdom and establish in nature a 5 38207 6 Can Science Explain Life? sharp line of demarcation between living and non- living things. Although growth and reproduc- tion, in their broadest aspect, amount to nothing more than self-duplication, yet they are funda- mentally different from any of the other processes heretofore known to science. Biological growth does not proceed in the same manner as the growth of crystals because exten- sive chemical transformations take place during the process of metabolism whereas the growth of crystals involves no permanent chemical change whatever. It also differs from crystal growth in that the assimilation of food by the cells of living organisms does not require saturated solutions such as are necessary for the growth of crystals. Another difference is in the final result produced, for although biological growth can produce or- ganisms of the utmost complexity and variability and generally of rounded contour, yet crystal growth produces only such structures as are of angular contour, internally homogeneous, and neither complex nor variable. Biological reproduction, or more specifically cell division, involves more than mere dispersion or subdivision because the progeny retain, either actually or potentially, not only the chemical com- position but also the specific physical organization of the parent cell. Neither can cell division be Introduction 7 regarded as merely a form of dissociation because the progeny of living organisms are structurally similar to the parent, whereas the particles which result from chemical dissociation are always dis- similar from the undissociated molecules. The ultimate cause of life, whether it be a cer- tain substance or a specific detail of physical structure, must be the same for all living organ- isms because the specific differences which distin- guish one living organism from another disappear as we go down the scale of plant or animal life. Since there are innumerable species of bacteria which exhibit no internal heterogeneity what- ever, even under the most powerful magnifica- tion, it appears that the ultimate units of liv- ing matter must exist on a scale smaller than the limit of microscopic vision, which is about 1/50,000 cm = 2,000 Angstrom units. Since the largest organic molecules which have been pre- pared synthetically measure about ten Angstrom units (10X10 -8 cm) across, it is evident that the ultimate units of living matter must exist in a region where we come dangerously close to the details of chemical structure, and that the ulti- mate cause of life must be looked for in the realm of chemistry rather than in the realm of physics. That the fundamental life processes must be due, either wholly or partly, to specific chemical 8 Can Science Explain Life? structures is generally admitted, but there is a prevailing opinion that the chemical configura- tions which are necessary for this purpose must be extremely complex. The failure of all pre- vious efforts to devise some type of chemical structure which is capable of duplicating itself does not prove, however, that the solution of the problem must lie in the direction of extreme com- plexity. The complex chemical structures which make up the tissues of the higher plants and ani- mals have developed gradually during the course of evolution, and the fact that they are necessary for the proper physiological functioning of the particular organisms in which they now occur does not prove that they were also the original cause of the incipient life processes in the most primitive submicroscopic forms of life from which these higher plants and animals have developed. With the exception of certain plasmodia and syncytia which have no definite cell walls, the bodies of all higher plants and animals consist of aggregates of separate living cells, all of which are constituted according to the same general plan in that they all consist of an outer cytoplasm which may contain central bodies, asters, fibrillae, plastids, Golgi-bodies, etc., and an inner nucleus which may contain chromosomes, linin network, etc. Nucleated cells like those which form the Introduction 9 bodies of the higher plants and animals have a definite lower limit of size, being never smaller than several (approximately five) microns in diameter. ( 1 micron = 1/10,000 cm = 10,000 Ang- strom units.) Since the diameter of the benzene ring, as measured between the centers of the carbon atoms, is about three Angstrom units (3 X 10" 8 cm) in diameter, it would require a series of about 17,000 benzene rings to extend across the smallest nucleated cell. It is probably safe to say that a structure of such complexity could never have sprung into existence spon- taneously from inorganic substances. The con- clusion is therefore inevitable that the typical nucleated cell does not represent the most primi- tive form of life, but is probably the final result of a long process of evolution. A much more primitive form of life is exhibited by the bacteria which carry on the same processes of metabolism and pass through the same cycles of growth and cell division as their nucleated rela- tives so that they must be regarded as true living organisms. Bacteria differ from nucleated cells in that they are definitely smaller in size, are usually formed to resemble some simple geo- metric figure, do not contain distinct chromo- somes, centrosomes, or other self-perpetuating 10 Can Science Explain Life? bodies, never conjugate, and never develop into multicellular organisms. The existence of a definite gap in size between the smallest nucleated cells and the largest bac- teria indicates that bacteria represent a distinctly different form of life from nucleated cells, and when we consider the extreme simplicity of their forms and the homogeneity of their internal struc- tures we feel inclined to believe that they consti- tute the most primitive class of living organisms. Even the largest of them are not far above the limit of microscopic vision, and there is every reason to believe that there are innumerable species which are similar in form and constitution to their larger representatives, but which are too small for the microscope to reveal. In order to avoid a confusion of issues at the outset, we shall for the present confine our atten- tion as much as possible to the bacteria because these exhibit the fundamental life processes in their simplest phases. The problem of explain- ing life does not require that we should furnish an explanation of the entire process of evolution, but only of those processes and characteristics which are common to all forms of life and which must have been exhibited by the most primitive form of living matter as it first appeared on this earth. THE CHEMICAL BASIS OF LIFE There being no evidence to justify us in assum- ing that life processes are due, primarily, either to specific details of physical structure or to ex- treme complications of molecular structure, we find ourselves driven to the conclusion that life processes must be due to some comparatively simple principle of chemistry which has not yet been discovered. To find a clue to this we must investigate the chemical structure of proteins, because protoplasmic materials which are prin- cipally of protein constitution appear to consitute the basis of all life processes. Fats and carbo- hydrates, although formed during protein metab- olism, are evidently nothing more than by-prod- ucts which may be useful at times for fuel or skeletal support and may by their presence exert the most profound effects upon the behavior of the surrounding protoplasmic materials but are not chemically constituted in such a manner that they can grow or reproduce. All proteins decompose hydrolytically upon prolonged boiling with hydrochloric or sulphuric acid or with alkalies, upon treatment with super- heated steam, or upon treatment with certain enzymes such as pepsin or trypsin, and yield as their principal cleavage products a mixture of 11 12 Can Science Explain Life? amino acids or their anhydrides (diketopiper- azines), which may be represented generally as follows : CO— OH CO— NH / / \ -CH or — CH CH- \ \ / NH 2 NH— CO About thirty of these amino acids or their anhy- drides have been isolated, the structural formulas of the more important ones being as follows : H c= =N / \ CH CH \ / Nr =C H Aliphatic monobasic monamino acids • Glycine CO— OH H— CH \ NH 2 Alanine CO— OH / CH 3 — CH \ NH 2 Valine CH 3 CO— OH \ / CH— CH / \ CH 3 NH 2 Isoleucine CH 3 - -CH 2 CO— OH \ / CH— CH / \ CH 3 NH 2 The Chemical Basis of Life 13 Leucine CH 3 CO— OH \ / CH— CH,— CH / " \ CH 3 NH, Caprine GH 3 — CH 2 — CH 2 — CH 2 — CH CO— OH NE Aromatic monobasic monamino acids: Phenylalanine Tyrosine Dibasic monamino acids, Aspartic acid Glutamic acid Monobasic diamino acids, Arginine NH \ H H C=C CO— OH / \ / HC C— CH,— CH \ // \ C— C NH 2 H H H H C=C CO— OH / \ / HOC C— CH 2 — CH \ // \ C— C NH 2 H H / CO— OH / CH,— CH HO— OC \ NH 2 HO- -OC CH 2 — CH 2 -CH \ CO— OH NH, NH 2 C— NH CH,- -CH,— CH,— CH CO— OH / \ NH 2 14 Can Science Explain Life? Ornithine NH 2 CO— OH \ / CH 2 — CH> — CHo — CH NH 2 Lysine NH 2 CO— OH \ / CHo — CH> — CHo — CH 2 — CH NH, Hydroxy- and Thio-amino acids: Serine CO— OH HOCH 2 — CH NH 2 Hydroxyglutamie acid H CO — OH CH 2 — CH— CH / \ HO— OC NH 2 Cysteine CO— OH HS— CH— CH \ NH 2 Cystine NH 2 CO— OH CH— CH 2 — S— S— CH 2 — CH / \ HO— OC NH 2 Glutathione (y-glutamylcysteylglycine) CO— OH / HO— OC CH 2 CO NH \ S/ ^CH— CH 2 — SH CH— CH 2 — CH 2 NH CO NH 2 The Chemical Basis of Life 15 Heterocyclic amino acids, Proline Hydroxyproline Histidine CO— OH / CH 2 — CH / \ CH 2 NH / CH 2 CO— OH CH 2 — CH y \ HOCH NH \/ CH 2 H CO— OH \ / H C— CHo— CH XN N X NH 2 IN Tryptophane NH- CO— OH CH- // // CH \ CH==CH -CH \ / -C C— CH 2 — CH \ / \ C HH 2 / Anhydrides : Leucine anhydride CH 3 CO— NH CH 3 ^ / \ / CH— CH 2 — CH CH— CHo— CH / \ / \ CH 3 NH— CO CH 8 Because of their frequent occurrence in living tissues, the formulas of the following substances should also be given. 16 Can Science Explain Life Aspargine Glutamine NH 2 — CO CO— OH / CH 2 — CH / \ NH 2 — CO NH 2 CO— OH / CH 2 — CH 2 — CH / \ NH, Creatine Uric acid Plant nucleic acid (Phosphoric acid Animal nucleic acid / Phosphoric I acid Lecithin CO— OH / H— CH \ N C=NH / I CH 3 NH 2 NH— CO CO C— NEX CO NH— C— NH/ \ / Guanine \ d-Kibose J I CjtosZ ) / 4 \ Uracyl / / \ / Guanine / Desoxy- \ / Adenine I ribose I I Cytosine \ A \ Thymine, CH 3 CH 3 R"CO O -P— O— CHo— CH— CH 2 O K'CO CH 3 O O H 26.0 0.02 0.0 8.7 2.0 0.2 4.2 The Chemical. Basis of Life 17 Kephalin R"CO O O NH 2 - CH 2 — CH 2 — O— P— O— CH 2 — CH— CH 2 o o H R'CO Approximate Percentage Yield of Amino Acids from Proteins Egg Ca- Edes- Fi- Gela- Glia- Hemo- Albumin sein tin brin tin din globin Glycine 0.0 0.5 3.8 3.0 Alanine 8.1 1.5 3.6 3.6 Valine 2.5 7.0 6.2 1.0 Isoleucine 1.4 11.0 21.0 15.0 7.1 5.6 30.0 Leucine 7.9 Phenylalanine... 5.1 3.9 3.1 2.5 Tyrosine 1.8 5.0 2.1 3.5 Aspartic acid 2.2 1.4 4.5 2.0 Glutamic acid... 9.1 15.8 19.0 10.0 Arginine 4.9 4.5 15.0 4.7 Lysine 3.8 6.0 2.0 11.0 Serine 0.0 0.4 0.3 0.8 Cystine 0.3 0.02 1.0 1.2 Proline 3.6 7.0 4.1 3.6 Hydroxyproline 0.2 2.0 Histidine 1.2 3.0 2.0 6.4 Tryptophane + 1.5 0.4 1.3 + + The accompanying table gives the percentage yields of the various amino acids from certain proteins, but these values should be interpreted 1.4 2.4 4.2 0.01 1.2 1.3 3.4 0.58 4.4 5.8 37.0 1.7 8.2 . 3.2 5.4 5.9 0.0 4.3 0.4 0.13 0.6 0.45 0.3 9.5 7.1 2.3 14.0 1.0 0.9 0.61 11.0 18 Can Science Explain Life? cautiously because it has never been proved that amino acid molecules exist as such in proteins, even in peptide combination. As will be ex- plained in the subsequent chapters, they probably originated as torn-off fragments which became dislodged from the fabricated protein structure during hydrolysis, and whether the dislodged fragments are of one size or another may depend not only on the chemical structure of the protein but also on the nature of the hydrolyzing agent. There is, in fact, only very little justification for employing the molecular concept at all in our con- sideration of proteins. The molecular theory was invented for the explanation of the definite and sometimes simple proportions by weight or vol- ume in which certain substances react, but the ex- periments on which the molecular theory were based did not include experiments with proteins, the combining proportions of which are neither definite nor simple. Those proteins which are soluble in water may consist, not of particles, but of fibrous networks as is evidenced by the opal- escence and stringyness of their solutions and by many of their other physical and chemical proper- ties, whereas those which required special re- agents to dissolve them were probably trans- formed chemically during the process, so that The Chemical Basis of Life 19 they are no longer identical with the substances which exist in living cells. The vulnerability of proteins to even the most gentle chemical treat- ment is well illustrated by the treatment of hair for a short time with dilute hot sodium carbonate solution, which will reduce the cystine yield from about three percent to almost nothing. If an indi- vidual fiber of protein can be called a "molecule" merely because it represents the smallest state of subdivision in which that substance exists in nature, then it appears that a single fiber of cotton should also be called a "molecule." By suitable chemical treatment the above-men- tioned amino acids can be condensed, with the elimination of water, to form either chain struc- tures known as polypeptides or ring structures known as diketopiperazines : 3 NH 2 — CHE^CO— OH = NH 2 — CHE^CO— NH— CHE— CO— NH— CHEr-CO— OH + 2 H 2 0; 2 NH 2 — CHEr— CO— OH = CHEr— CO / \ NH NH + 2 H 2 0. \ / CO— CHE Numerous methods for preparing polypeptides have been devised by Emil Fischer and his col- 20 Can Science Explain Life? laborators in Germany, and molecules containing as many as nineteen amino acid groups have been prepared. There is an abundance of evidence that the peptide linking — CO — NH — occurs in the pro- tein materials of all living cells. For example, the same pink or violet color (the biuret reaction), which is produced from this linking in any of the higher polypeptides by the addition of an excess of sodium hydroxide and a trace of copper sul- phate is also produced upon the addition of these reagents to proteins. Polypeptides and proteins also produce the same amino acids when heated with mineral acids or alkalies, so that they must contain the same structural units. That the amino acid groups in proteins are connected by means of peptide linkings is also evidenced by the fact that all proteins which have not been previously treated with mineral acids or alkalies form neutral solu- tions, so that the number of free carboxyl groups must be equal to the number of free amino groups. The fact that only a small fraction (usually less than ten percent), of the total protein nitrogen can be separated as free amino nitrogen shows that most of the amino groups of the original amino acid molecules must have become modified or occupied in some manner at the time when The Chemical Basis of Life 21 these amino acids were assimilated by the proto- plasmic materials, and it is inconceivable how the removal from the field of action of exactly equal numbers of amino and carboxyl groups could be explained in any other manner than by the forma- tion of peptide linkings. From considerations such as these the conclu- sion has generally been reached that the proto- plasmic materials of living cells grow by the for- mation of peptide linkings with amino acid mole- cules, so as to produce either the chain structure of polypeptides or the ring structure of diketo- piperazines. It was formerly thought that the structure thus produced was entirely of poly- peptide nature, but more recent investigations have shown that diketopiperazines are always present among the hydrolytic cleavage products of proteins, even under conditions which would render their synthetic formation from the initially produced polypeptides highly improbable. How- ever, the chemical structures of the solid or col- loidal protoplasmic materials which have been subjected to hydrolysis may not be identical with the molecular structures of synthetically prepared polypeptides, even though they may both contain peptide linkings, and with our present scanty knowledge of protein structure we would not be 22 Can Science Explain Life! justified in assuming, without further proof, that this difference in chemical structure between pro- teins and polypeptides would not be sufficient to explain the subsequent formation of diketo- piperazines when proteins are subjected to hy- drolysis. That diketopiperazines are not nor- mally present in most proteins is also evidenced by the fact that neither pepsin, tripsin, nor erepsin will split the diketopiperazine ring. But regardless of whether or not the diketo- piperazine ring is present in proteins, it appears, from biological considerations, that neither the simple polypeptide structure nor the unaltered diketopiperazine rings are adequate for the pur- pose, either singly or in juxtaposition. Neither of these structures shows any tendency to grow spontaneously by assimilation of amino acid mole- cules, or to divide spontaneously into daughter structures which either possess or acquire the same specific structural organization as the par- ent. The persistence with which living organisms will devour every bit of food material within reach and invade the entire earth's surface with their progeny shows that they must possess within the chemical structures of their tissues some con- trivance which is definitely superior to ordinary chemical forces and which can function in a man- The Chemical Basis of Life 23 ner unknown to chemical science. What is needed for this purpose is not some new form of molecule but some new type of chemical structure; not some new arrangement, but some new principle of atomic behavior. SPIRAZINES One of the most remarkable characteristics of living organisms is that all normal physiological functions can take place while growth is in prog- ress. In this respect living organisms differ from artificial contrivances, which usually cannot per- form their intended functions while they are in the process of construction. Kegardless of whether we are considering a multicellular or a unicellular organism, its physical behavior does not seem to bear any direct relationship to the chemical activ- ity of the growing protoplasmic materials of which it is composed. This peculiar independence of behavior and growth can be explained only on the theory that the specific structural character- istics of protoplasmic materials are not changed, either physically or chemically, by the addition of amino acid molecules thereto. If the protoplasmic structures of living cells were built up of discrete molecules of utmost com- plexity, as is generally supposed, then it would be impossible to explain the process of growth which in nature takes place continuously and spon- taneously by the assimilation of one amino acid molecule after another. The synthesis of complex 24 Spirazines 25 molecules can never be accomplished by one con- tinuous process, but even if it could be thus accom- plished there would have to be an abrupt change in the nature of the process after the completion of one molecule in order to initiate the formation of the next one. However, there is no experimental evidence that the protoplasmic structures of living cells are built up of discrete molecules, or that they are of utmost chemical complexity. In regard to their supposed molecular constitution, it might be stated that most proteins, and especially those which form the nuclear or actively growing por- tions of living cells, require special chemical treatment to bring them into solution, whereas those which will dissolve in water, as for example the albumins, are probably no longer integral portions of the cell structure but may consist of free colloidal bodies which have grown out from the nuclear material and have become detached. In regard to their supposed chemical complexity, a distinction should be made between two-dimen- sional complexity and three-dimensional complex- ity. Although it seems impossible to explain growth and reproduction if we assume that proto- plasmic materials possess three-dimensional com- plexity, yet it seems comparatively easy to ex- plain these processes if we assume that they 26 Can Science Explain Life? possess only two-dimensional complexity and that the third dimension is built up by mere super- position of layers having the same arrangement of atoms. Growth and reproduction being the two indis- pensable processes without which life is incon- I o - Fig la. — Fig, lh. Spirazines 27 I Q 5 r/5. id. ceivable, the chemical structure of living matter from which such life processes seem to originate must possess the two following characteristics : (1) It must be of such a nature that the process of growth by the formation of peptide linkings with amino acid molecules can take place con- 28 Can Science Explain Life? l 5 Fid. le. tinuously without producing any abrupt change in its external chemical configuration ; and (2) It must be capable of division into a plu- rality of portions each of which retains either actually or potentially the complete pattern of the original structure. Spirazines 29 Of the various geometric forms which chemical structures might exhibit, the helical spiral ap- pears to be about the only one which possesses characteristics similar to those mentioned above, and it appears that the helical spiral is also the only configuration, besides rings and chains, which the polypeptide molecule can be made to assume. The ease with which diketopiperazine rings are formed from dipeptides, and the diffi- culty of splitting such rings, seems to indicate that the valencies of the successive carbon and nitrogen atoms in dipeptides are at such angles to one another as to give them a natural tendency to form six-atom rings ; and if dipeptides tend to form six-atom rings, then polypeptides would tend to form spirals with six-atom convolutions, which will be referred to, briefly, as "spirazines." It will be observed that one of the valencies of the alpha carbon atom in these amino acids is always occupied by hydrogen. Chemically it would be possible to attach more complex groups in this position, but it will be found upon experi- mentation with atomic models that the presence of more complex groups in^this position would render the spirazine structure impossible, and it will be observed that complex groups never occur in this position in the decomposition products of natural proteins. 30 Can Science Explain Life? The two ends of such a spirazine will be differ- ent in that one end will be formed of an acid carboxyl group whereas the other end will be formed of a basic amino group. When the dis- similarity of chemical structure at the two ends is taken into consideration, it seems highly im- probable that the ability to grow by assimilation of amino acid molecules could be possessed by both ends alike. The fact that the physiological effects of different substances when injected into the blood stream are due almost entirely to the positive kations seems to indicate that assimila- tion in animal cells takes place at the carboxyl ends only, although the acid character of the chemically active portions of living matter may also be due to phosphoric acid radicles clinging to the amino groups at either end of the spirazine, and acting catalytically as intermediaries to facili- tate the assimilation of amino acid molecules, just like sulphuric acid acts catalytically to facilitate the combination of alcohols with organic acids to form esters. The fact that phosphorus occurs principally in the nuclear materials where such assimilation is known to take place, and even there only in comparatively small amounts, seems to indicate that it does not enter permanently into the interior of the chemical structure of proto- Spirazines 31 plasmic materials but is associated only with the actively growing portions thereof. The successive nitrogen atoms along each side of the spirazine will increase the basicity of the terminal nitrogen atom, just like the two nitrogen atoms in diazo compounds increase the basicity of each other. Similarly the carbonyl groups along each side of the spiral will increase the acidity of the terminal carbonyl group. We thus have a strongly basic group held firmly in close prox- imity to a strongly acid group without being per- mitted to neutralize the same, which may account for the remarkable ability of living matter or its enzymes to digest all sorts of complex food ma- terials and to appropriate the resulting sub- stances spontaneously and continuously for the building up of its own protoplasmic structures. If the successive nitrogen atoms in a spirazine are joined to one another by means of their fourth and fifth valencies in the manner shown, which seems to be entirely possible by reason of the fact that these valencies in amino compounds are always of opposite sign, then it appears that at least some of the nitrogen atoms in proteins are really pentavalent and should therefore be in- capable of forming hydrochlorides in stoichio- metric proportions as in the case of polypeptides. This is in complete agreement with experimental 32 Can Science Explain Life? facts, for it has been found that the amounts of hydrogen chloride gas which are taken up by pro- teins are much smaller than the amounts which they should take up if they were ordinary poly- peptide structures. On the other hand, the amount of acid which a protein is capable of neutralizing is always much greater than the amount which could be taken up by the terminal — NH 2 groups, which never con- tain more than about ten percent of the total protein nitrogen. Similarly the amount of base which a protein is capable of neutralizing is always much greater than the amount which could be taken up by the terminal — CO — OH groups, assuming these to be about equal in num- ber to the — NH 2 groups. It must therefore be concluded that the ability of proteins to neutralize acids and bases is due not only to the terminal amino and carboxyl groups, but also, in a large measure, to the peptide groups — CO — NH — along the sides of the spirazines. In the spirazine structure shown in Figs, la and lb, the alternate peptide groups are connected to one another by means of the fourth and fifth valencies of the nitrogen atoms, and also by means of the oxygen atoms, but these connections are probably not very permanent and may change over into the enol-form shown in Figs, lc and Id, Spirazines 33 or into the keto-f orm shown in Figs, le and If. It would probably not be possible for acid or basic radicals to attach themselves to the sides of the spirazines and become neutralized while the con- figuration shown in Figs, la and lb exists, but such neutralization should be possible as soon as the structure changes over to the configurations shown in Figs, lc, Id, le, or If. The relation of these tautomeric changes to the chemical and physical behavior of protoplasmic materials of- fers a promising field for further speculation, but cannot be taken up in detail in the present brief discussion of this subject. Life probably commenced with the spontaneous formation of di- and tri-peptides from inorganic substances. The process may have commenced with the spontaneous formation, at high tempera- tures, of small quantities of acetylene CH = CH. Unsaturated compounds of this sort will readily form addition products and may have produced glycine or other amino acids. For example, the acetylene may have combined with water in the presence of dilute sulphuric acid to form acetalde- hyde CH 3 • CHO, and the acetaldehyde may have polymerized into aldol CH 3 ■ CHOH • CH 2 CHO which will also occur spontaneously at ordi- nary temperatures in the presence of dilute 34 Can Science Explain Life? acids or salts. At higher temperatures the aldol may have been converted into crotonaldehyde CH 3 • CH : CH • CHO by the loss of a molecule of water and the latter may have become oxidized to crotonic acid CH 3 CH : CH • COOH. Since cro- tonic acid contains a double bond, it could easily have been converted into the corresponding amino acid CH 3 ■ CH 2 • CHNH 2 • COOH either by direct addition of ammonia or by combination with some oxide or acid of nitrogen and subsequent reduc- tion. The amino acid molecules may then have been converted into polypeptides by the action of dry heat, and the latter, under suitable conditions, may have formed the first spirazines. The individual spirazines thus produced may then have developed into more complex structures by folding over upon themselves as will be de- scribed more in detail later. Endwise growth of such structures may then have taken place either by assimilation of complete amino acid molecules which may have been present in the surrounding medium, or by the spontaneous synthesis of the alpha amino acid structure from the carbon di- oxide, water, and nitrogen compounds in the sur- rounding medium, such synthesis having probably been effected by the catalytic action of the spira- zines themselves in the presence of sunlight. Although there is no experimental evidence that Spieazines 35 the evolutionary development of living matter actually began in the specific manner above sug- gested, nevertheless, it appears from the fore- going example that the spontaneous formation of spirazine structures from inorganic substances under conditions which actually existed in nature may be readily explained on the basis of known experimental facts. The similarity in form and appearance of these primitive hypothetical structures to the various lower or elementary forms of life, such as the fila- mentous bacteria, connective tissue fibers, and nerve fibers, will be apparent. In each case the cross-sectional pattern will be the same at any point along the length and comprises not only the arrangement of the spirazines with respect to one another but also their directions of twist. This pattern will be characteristic of the species and upon transverse fission will be transmitted to the progeny. The possession by the spirazine structure of a definite direction of twist will also account for the optical activity which is always exhibited by substances obtained from living organisms, and also for the partiality which is usually shown by living organisms towards one optical isomer over another. In living organisms chirality is the rule rather than the exception, and can be accounted 36 Can Science Explain Life? for only on the basis of an inherently twisted structure such as the spirazines possess. It is an interesting fact that all proteins which have not been subjected to too severe chemical treatment will rotate the plane of polarization of light to the left. The fact that animal proteins have the same direction of rotation as vegetable proteins might be accounted for on the theory that since animals either feed upon plants directly, or upon other animals which do feed upon plants, it might be expected that the structural materials of plant and animal tissues would exhibit some fea- tures in common. It is not so easy, however, to explain why all plant proteins rotate the plane of polarization to the left, unless we are willing to admit that all the present species of plants have descended, not only from a single ancestral spe- cies, but also from a single spirazine. Such an assumption should not be summarily rejected as unreasonable unless we can find some other way of explaining the uniform optical properties of all proteins. If there would be only a few of them, it might be attributed to coincidence ; but since the number of proteins whose optical properties have been determined runs into hundreds, the possi- bility of it being due to mere coincidence must be ruled out. PROTOPLASMIC STRUCTURE Since a single spirazine, being of about the diameter of a benzene ring, measures only about three Angstrom units (3 X 10~ 8 cm) between the centers of the atoms on opposite sides, it is evi- dent that even the smallest bacteria, and all other fibrous forms of living matter which are visible under the microscope, must consist of aggre- gates of large numbers of spirazines. The large amounts of water which protoplasmic materials always contain, and the rounded forms which the simplest units of living matter always exhibit, seem to indicate that the spirazines thereof are not arranged in closely packed formation like the molecules of a crystal, but rather in some sort of open or spaced-apart formation. Chemical union between adjacent spirazines can take place only through the amino, the carbonyl, or the alpha carbon groups, because these are the only groups that are present. Any two adjacent spirazines must therefore be connected, directly or indirectly, in one of the following ways : Amino nitrogen to amino nitrogen; Amino nitrogen to carbonyl carbon; Amino nitrogen to alpha carbon; 37 38 Can Science Explain Life! Carbonyl carbon to carbonyl carbon; Carbonyl carbon to alpha carbon; Alpha carbon to alpha carbon. Any of the above unions, except those which involve direct connections between nitrogen and nitrogen or between nitrogen and oxygen, would be chemically stable, but their stability alone does not prove that they exist in nature. Protoplasmic materials have not resulted from a promiscuous mixture of the elements, but from an orderly and systematic process of evolution in which only those configurations have survived which have conformed to the dominating influence of the spirazines. It appears from the chemical struc- tures of the various protoplasmic decomposition products that only the following unions between adjacent spirazines occur in nature : (1) Direct union of amino nitrogen to car- bonyl carbon, as evidenced by the urea and guanidine complexes; (2) Direct union of alpha carbon to alpha carbon, as evidenced by aspartic acid (doubt- ful); (3) Indirect union of alpha carbon to alpha carbon by means of one, two, or three — CH 2 — groups, as evidenced by glutamic acid, argi- nine, and ornithine, respectively. Protoplasmic Structure 39 (4) Indirect union of alpha carbon to alpha carbon by means of the — CH 2 — S — S — CH 2 — group, as evidenced by cystine. The above conclusions were arrived at on the assumption that protein nitrogen occurs only in the spirazines. There is no evidence that it occurs anywhere else, and the amount of nitrogen that is present in the spirazines alone is too much rather than too little to satisfy the percentage composition of proteins as found experimentally. The two amino groups of arginine, ornithine, and lysine were therefore assumed to have come from adjacent spirazines. The hydrocarbon side chains of amino acids exhibit frequent branching at the beta and gamma carbon atoms, as in the case of valine, isoleucine, leucine, phenylalanine, and tyrosine. Such branch- ing, at first glance, suggests triple junctions be- tween three adjacent spirazines as shown in Fig. 2. Such triple junctions would undoubtedly be chemi- cally stable and will fit together nicely to form hexagonal compartments as shown in Fig. 3, which would probably be able to grow and perpetuate themselves if they actually existed. However, if such structures exist in nature, then the decompo- sition products of protoplasmic substances ought to contain tri-amino or tri-carboxylic acids or 40 Can Science Explain Life? A Triple Junction of the Wy-Type. some derivatives thereof, whereas no such com- pounds have ever been found. It appears, there- fore, that we would not be justified in assuming the extensive existence of triple junctions of this type, notwithstanding their adaptiveness for the building up of three-dimensional structures. Protoplasmic Structure 41 Fig 3. Hexagonal Compartments The manner in which the adjacent spirazines of protoplasmic structures became connected to one another in nature must have been intimately re- lated to the evolutionary development of living matter. The linking of adjacent spirazines with one another may have resulted either from polym- erization of separate spirazines or from the fold- ing over of the individual spirazines upon them- selves. If it resulted from polymerization, then 42 Can Science Explain Life? combinations of right-handed and left-handed •spirazines should have occurred frequently, and the number of optically right-handed combina- tions should have been about equal to the number of optically left-handed combinations. However, since nearly all proteins are left-handed, it must be concluded that the evolutionary development of protoplasmic structures could not have taken place by random polymerization but was probably brought about by some sort of folding over process. ' H 'h ^