METABOLITE ANTAGONISTS The Relation between Structure and Biological
Chemical Activity
R I C H A R D O. R O B L I N , J R . , C h e m o t h e r a p y Division, S t a m f o r d R e s e a r c h L a b o r a t o r i e s , American Cyanamid Co., Stamford, Conn.
T h e recognition of antagonists structurally related t o various metabolites has stimulated the interest of both chemists a n d biologists in recent years · · . T h e origins a n d n a t u r e of this concept a n d its u s e f u l n e s s a n d l i m i t a t i o n s a r e o u t l i n e d i n t h i s r é s u m é
J. HE development of a general concept may proceed independently along several linos of investigation until it is suddenly recognized as a relationship common to a number of different systems. This sudden recognition is sometimes the result of a particularly striking illustration of the general effect, and such appears to have been the case for the metabolite antagonist or antimetabolite concept. Observed independently in such fields as onzymology, pharmacology, and chemotherapy, it emerged in a generalized form (/) only after providing a basis for the demonstration of the mechanism of action of the sulfa drugs (2). With this demonstration of the now familiar relationship between p-aminobenzoic acid and the sulfanilamides, the concept became a strong stimulus to research, and metabolite antagonists the popular subject of hundreds of subsequent investigations (3). As a consequence, it may be of interest to inquire into the evolution and current status of metabolite antagonists, together with the criteria necessary for their critical evaluation. Term* Defined In this discussion a metabolite may be any substance essential to chemical processes by which living cells are produced and maintained. It may be synthesized by the cells or obtained from their environment. Antagonists are substances which block or inhibit the normal function of a metabolite. Although several types of antagonisms have been observed, those involving a close structural relationship between the metabolite and the antagonist have been by far the most stimulating. Consequently, the emphasis in this résumé will be largely on antagonisms of this type. 36S4
In the field of enzymology the inhibitory effect of substances structurally related to the substrate was recognized years ago (4). An oft-cited illustration is the inhibition of the enzyme succinic dehydrogenase by malonic acid (5) : HOOCCH8COOH
HOOC(CH 8 ) 2 COOH
Malonic Acid
Succinic Acid
This complex may also break up to re lease free enzyme and the product or products of the reaction. The antagonist or inhibitor, /, also forms a reversible complex which ties up a fraction of the enzyme. Consequently, the constant or inhibition index, K, is dependent on the relative concentrations of metabolite and antagonist, rather than on the abso lute concentrations of either. When the antagonist inhibits bacterial growth, which is also dependent on enzymic re actions, the constant is referred to as the antibacterial index. A number of antagonisms were investi gated by pharmacologists (6), who found that substances inhibiting certain of the effects of acetylcholine and epinephrine
The homologous dibasic acid is assumed to inhibit the enzyme by competing with the normal metabolite, succinic acid, for the "hot spots" or active centers on the enzyme surface. These centers are thought to be oriented specifically to pick up succinic acid as a preliminary to its dehydrogenation. While highly specific, the active centers may also adsorb closely related molecules such as malonic acid. When both metabolite and antagonist are present, a competitive inhibition between them results in a more or less complete blocking of the enzymic reaction, depending on their relative —12.4 A. 1 -H2.3Â.|«concentrations. The following equations illusp-Aminobenzoate Ion Sulfanilamide trate this effect in terms 1. Interatomic distances and Fig. of the mass action equistructural relationships librium : E + Sz±ES—>E K
=
LSI * [ËÏ] '
+ P; Ε + I ^ EI at 5 0
^
inhibition
>
[ES] = [EI], and Κ - jjg In such a reaction the substrate or metabolite, S, is assumed to form a re versible complex with the enzyme E. CHEMICAL
appeared to act by a competitive mecha nism. Their results could also be inter preted in terms of a mass action effect. The structural resemblance between the metabolites and their respective antago nists led to the suggestion in 1937 that substances are most likely to be antago nized by compounds of a similar molecu lar configuration (6). AND
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Table I. Effects of Antagonist and Metabolites on Growth of 5 . faecalis (Ralston) Metabolites. 1
•y/Cc for / 2 Maximal Growth
Antagonist, Sulfadiazine, •y/Cc. 1 10 100 1000
Tryptophan X any quantity of 4m e t hylanthranilic Fig. 2 . Biosynthesis of tryptophan acid. Supplying the product of the re action again, as in sulfa drugs is given in Table I. Again certain cases with folic acid, eliminates with a limited group of microorganisms, the necessity for the reaction altogether. the minimum amount of folic acid neces Tryptophan, in this instance, produces sary for growth will prevent the anti the same result. In a similar manner, bacterial action of any amount of sulfa 4-methylindole antagonizes the synthesis diazine. This is a noncompetitive re of tryptophan and, under proper condi versal so that a constant index is not tions, inhibits the growth of bacteria. obse£',£ed. Presumably, supplying the The growth inhibition can be relieved product of the blocked reaction elimi competitively by the addition of indole, nates the reaction as an essential for the or noncompetitively by tryptophan. The growth of the organisms. The same re growth inhibition can be relieved com sult has not been obtained with the petitively by the addition of indole, or majority of microorganisms, however, noncompetitively by tryptophan. The and this complication will be discussed methyl tryptophans, in turn, act as subsequently. competitive antagonists of the further utilization of tryptophan. Other illustrations Metabolite antagonists found among In recent years, as a result of the compounds structurally related to biostimulus and generalization provided by tin are synthesized by certain organisms the demonstration of the p-aminobenfrom desthiobiotin by the unique method zoic-sulfanilamide relationship, numerous shown in Fig. 3. analogs such as the vitamins, hormones, Fig. 3. Synthesis of biotin 1 amino acids, purines,
Folic Acid amides might be due to their interfer ence with the utilization of p-aminoben zoic acid for the synthesis of folic acid. This suggestion is borne out in one direc tion by the existence of certain organisms which require preformed folic acid for growth. These organisms are unable to synthesize their own supply of the vita min from p-aminobenzoic acid and re quire an outside source for growth. They are also insensitive to sulfa drugs. Such a result might be anticipated, since one can hardly prevent organisms from 2 7,
c
C (p-ABA radical)
HOOC—CH
VOLUME
H
NH 2
H H HOOC—C—N— CH2
to
V"
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and pyrimidines have been prepared (3). Ex amples will serve to il lustrate the antimeta bolite concept. Some organisms have been shown to carry out the biosynthesis and fur ther utilization of tryp tophan, one of the es sential amino acids, as in Fig. 2. Further utili zation of tryptophan is
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1
HN
HN
NH
HC
CH
CH,
J
>OH CH2(CH2)4CC Desthiobiotin
NH
I
-* HP —• PH
1
H2C
V
CH(CH8)4COOH 1 Biotin
1
h
h Ι ΗΝ
ΝΗ
ΗΝ
J H2C
CH
HC
CH
H2C
CH—(CH2)4COOH
J 1 1
CH2(CH2)4COOH Imidazolidone caproic Acid
H2C
ΝΗ
CH2 ô-(2,3-Ureylenccyclohexyl)valeric Acid
1 1 1
3625
numerous metabolic processes which are interdependent, however, nature is not always so obvious. ' In other cases the re sults "are frequently more complex. Let us return to the sulfa drugs, for example. It was mentioned earlier that folic acid completely fails to prevent O their antibacterial action with a majority * of bacteria. So far no satisfactory ex \ ftH planation for this apparent anomaly has HN CH3SCH2CH2CHCOOH been advanced. It may be that most organisms, for one reason HC CH NH 2 or another, are unable to H2C CH—(CH2)4COOH Methionine utilize preformed folic acid. No/ Such an explanation would CH3OCH2CH2CrICOOIl be consistent with the fact Oxybiotin NH 2 that folic antagonists ap parently act only on the same relatively Mcthcixiniiu» small group of organisms with which the organisms by antagonizing their utiliza vitamin reverses the sulfanilamides. tion of biotin (18). Nevertheless, no conclusive evidence for Lest the reader be led to assume that this hypothesis has been advanced, and almost any structural modification of a alternative explanations, equally plau metabolite will lead to an antagonist, sible, can be suggested. In any event, attention is directed to oxybiotin, which, these observations illustrate one of the far from being a biotin antagonist, has baffling complications which has arisen bio tinlike activity (14) and is utilized by in these investigations. cells in place of biotin. On the other hand, replacing the sulfur atom in methi Apparent Anomalies onine by oxygen does lead to an effec Even such an apparently straightfor tive antagonist (15). ward case as the competition between in The antimetabolites discussed so far organic ions has led to some puzzling have been studied almost exclusively observations. Certain organisms have with microorganisms. However, anal been found to require potassium ion for ogous results have also been obtained growth in a chemically defined medium with some antagonists in experimental (IS). In the absence of Na* the require animals. For instance, in addition to its ment for K + is lower than when the growth-inhibitory action on certain former ion is present, and a competitive microorganisms, neopyrithiamine pro antagonism between the two closely re duces in rats typical symptoms of thia lated ions appears to be involved. For mine deficiency (16). If allowed to pro some of the organisms, Rb+ can replace ceed unchecked, the deficiency ends fa K + both as a growth factor and in revers tally in a relatively short time. When ing the growth inhibition produced by thiamine is also administered in adequate N a \ On the other hand, for another quantities, however, the animals do not organism Rb+ inhibits growth and K* re develop the deficiency. verses the inhibition. Cs+ is a K+ an tagonist in all the cases investigated. C 3 " C1W Ν While Li+ also inhibits growth, its effect —NH a X C—OH2CII2OH is not reversible by K+, but it is pre vented by a mixture of Na + and ΝΗΛ / These somewhat confusing results indi cate the subtle though crucial differences in the structure of enzymes from differ Thiamine ent sources which presumably have the C lî same* or similar functions (18). When Ν .* CFT2CH2OH one considers that, with the exception of !—NH2 / N H / , a differentiation is being made in Ν H the electronic stucture of elements from the same group in the periodic system, Br these observations seem all the more re markable. Neopyrithiamine Fig. 4 illustrates some of the complex Similar results with both micoorganinterrelationships involved in the syn isms and animals have been obtained us thesis and utilization of a vitamin such ing folic acid antagonists such as aminoas pantothenic acid. Several of these re pterin, in which an amino group replaces lationships have been suggested by the the hydroxyl of the folic molecule (17). use of metabolite antagonists. The steps Most of the illustrations cited thus far in the biosynthesis of coenzyme A, as have been relatively straightforward, and outlined in Fig. 4, involve the conversion the interpretation placed on the results of aspartic acid to /3-alanine; this sub has been quite plausible. Because of the stance plus pantoic acid or its lactone are Imidazolidone caproic acid, which differs from desthiobiotin by the lack of a methyl group, appears to interfere with the latter in the synthesis of biotin (11, 12), whereas the ureylenecyclohexylvaleric acid inhibits the growth of micro-
V
"° «—îCZ>
3626
CHEMICAL
converted to pantothenic acid which, in turn, is presumably incorporated in co enzyme A. The first step in this sequence is an tagonized competitively by cysteic acid (19), the monosulfonic acid analog of aspartic acid, as well as by hydroxyaspartic acid (20). The conclusion that aspartic acid serves as a precursor of /3-alanine is based on the observation that both this metabolite and panto thenic acid reverse the bacteriostatic effect of these aspartic antagonists. The reversing action of glutamic acid appears to be due to its role in the formation of aspartic from oxalacetic acid by trans amination. A large number of antagonists of the next step in the synthesis have been described in recent years (3). Only a few of these are indicated in the figure. /3-Aminobutyric acid, phenyl-j3-alanine (21), and some of the α-axnino acids (22) appear to compete with /3-alanine in the synthesis of pantothenic acid. In these cases, of course, the effect is re versed competitively by /3-alanine and noncompetitively by pantothenic acid. y - Hydroxy - /3, β - dimethylbutyric acid lacks one of the hydroxyl groups of pan toic acid and appears to compete with this metabolite in the synthesis of pan tothenic acid (23). With bacteria such as E. coli salicylate has the same effect (24). In these cases reversal can be brought about with pantoic or panto thenic acid. Curiously enough, pantoyltaurine, a pantothenate antagonist, also reverses the action of salicylate, presum ably because it is hydrolyzed to liberate pantoic acid (24). Antagonist Effect Depends on System With another biological system, E. coli bacteriophage, salicylic acid (o-hydroxybenzoic acid) seems to be an anthranilic (o-aminobenzoic) acid antagonist. At concentrations which do not affect bac terial growth, salicylic acid inhibits the multiplication of the bacterial virus, and this effect is reversed by anthranilic acid and tryptophan (25). Thus we have in this instance an antagonist which appears to be affecting the utilization of either pantoic or anthranilic acid, depending on the biological system involved. No specific metabolic relationship be tween guanine (26), or thiamine (27) and pantothenic acid has been estab lished. Although the reversal of the .antagoni&ti&.^£ipn of salicylic acid by these metabolites might suggesu~such a conclusion, the results may also be at tributed to a nonspecific effect on growth rate. The antibacterial action of many antagonists can be demonstrated only in simple media of known composition. Such conditions are frequently not opti mum for the growth of the microorgan isms, and the addition of any important metabolite which may be a limiting fac tor for growth in the simple medium AND
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m a y result in an increase in growth. U n less great care is exercised, this type of effect m a y be erroneously interpreted either as a specific reversal, of t h e growth-inhibiting action of a n anti metabolite, or as a demonstration of its lack of specificity. A number of antagonists affecting the utilization of pantothenic acid are known. Substances such as pantoyltaurine (2S), its amides {29), and phenyl pantothenone (30) have been shown t o inhibit the growth of various micro organisms. T h e former compounds bear the same structural relation to the vita min as sulfanilic acid and the sulfanil amides do to p-aminobenzoic acid. Phenyl pantothenone has the carboxyl group of pantothenic acid replaced by a phenyl ketone. The growth-inhibiting actions of these antagonists are reversed competitively by pantothenate. T h e o retically these antagonists should also b e reversed noncompetitively by coenzyme A, although so far n o such results have been reported. T h e effects of the ketone have b e e n reported to be reversed also b y several amino acids including glu tamic and aspartic acid (81). Were it not for the background of biochemical information previously available con cerning the metabolism of pantothenic acid, it might be even more difficult t o unravel the relationships outlined here. E v e n in this instance, some still remain t o be accounted for. Wl»!. other less well known systems, it is not surprising that the results are not always suscept ible to ready explanations. I n a few instances the antibacterial action of certain compounds appears t o be due t o the competitive inhibition of
a specific metabolite only with certain organisms, whereas with other species the antibacterial action is not reversed by the same metabolite. A case in point is found among certain ring-substituted sulfanilanilides such as the 3,5-dibromo derivative. With Gram-negative bac teria, the antibacterial action of this sub stance, like other sulfanilamides, is com petitively reversed by p-aminobenzoic acid. However, this metabolite does not affect the activity of the antagonist with Gram-positive organisms {32). Appar ently a different mechanism of action is involved with these bacteria, since strains with general resistance to sul fanilamides are still susceptible to the dibromonanilide derivative. Further evi dence is provided b y the fact that t h e re moval of the p-amino group, which with other sulfanilamide derivatives elimi nates antibacterial activity, does not ad versely affect activity i n this case. Finally, in another series, the pantoyltauranilides, the dibromo derivative ex hibits a bacteriostatic action which is only partially reversed b y pantothenic acid (29). Evidently sulfonamide deriva tives of dibromoaniline possess an anti bacterial action for certain organisms which is not directly related to the metabolism of p-aminobenzoic or panto thenic acid. An analogous situation may exist in the case of phenyl pantothenone and others of similar behavior. Criteria for Specific Antagonisms I t is evident that a number of factors must be considered in attempting to establish a specific antagonism. Even the observation that a substance acts as a specific antagonist in one biological
Fig· 4· Interrelationships
in synthesis
and
utilization
system cannot b e taken as a n y assurance that it is acting as a specific antagonist for another system in the absence of a demonstrable reversal. Neither struc tural resemblance nor the production of symptoms of a particular deficiency can substitute for the essential reversal test. Constant Ratio a Criterion Since nonspecific growth stimulation of microorganisms is frequently produced in synthetic media b y various metabo lites over narrow concentration ranges, the specific reversal should occur over a wide range of concentrations. Competi tive antagonism is, of course, character ized by a constant ratio between metabo lite and antagonist. I n addition t o a competitive reversal, it is important, if possible, to demonstrate that a second metabolite which is formed a t the next step in a series of metabolic reactions produces, in minimal effective concentra tion, a noncompetitive reversal of any reasonable quantity of antagonist (9). While in certain cases—for example, aminopterin—reversibility over only a small concentration range m a y be accept able because of the nature of the defi ciency, particular care in the interpreta tion of results is necessary in these in stances. Failure to· show any reversal with a particular metabolite should auto matically rule out consideration of a substance as a competitive antagonist for that metabolite in the biological sys tem under examination. Although it should be regarded as an essential test for a specific antagonism, reversal of the antagonism does not necessarily qualify the reversing agent as a metabolite. For example, it has been
of pantothenic
acid
NH2 HOOCCHCH 2 COOH
Inhibited b y : Cysteic Acid Hydroxyaspartic Acid
Aspartic Acid
Reversed b y : Aspartic Acid /3-Alanine Pantothenic Acid Glutamic Acid CH 3 H O C H 2 C C H 0 H C 0 0 H + H2NCH2CH2COOH CH3 Pantoic Acid
Inhibited b y : /5-Aminobutyric Acid Phenyl-0-Alanine «-Amino Acids «y-Hydroxy-0,0-dimethylbutyric Acid Salicylic Acid
/3-Alanine
CH 3
Reversed b y : £-Alanine Pantothenic Acid Pantoic Acid CH3 Pantoyltaurine Anthranilic Acid Pantothenic Acid Guanine Thiamine Inhibited b y : Pantoyltaurine and Amides Phenyl Pantothenone
HOCH 2 CCHOHCONHCH 2 CH 2 COOH
>• Coenzyme A
Reversed by: Pantothenic Acid α-Amino Acids
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known for many years that certain dyes interfere with the therapeutic effects of other dyes in trypanosome infections in experimental animals (33). Similar re sults have been described with arsenicals as well as other agents (34). In s o m e in stances a close structural relationship exists between the therapeutic agent and the interfering substance. Analogous re sults have been obtained in vitro, and attention has been directed to the fact that such interfering substances cannot be considered as metabolites on the basis of such evidence (35, 36). Moreover, in certain situations a known metabolite may reverse an antagonist without func tioning in its normal metabolic role. Thus p-aminobenzoic acid (37) and nicotinamide (38) reverse the trypano cidal action of some arsenoso compounds without appearing to function as m e t a b o lites at all. Although it is usually pos sible to rule out these cases without much difficulty, they must also be re cognized as an occasional complicating factor. These same factors are equally im portant when antimetabolites are em ployed as tools for the study of metabolic interrelationships. The evidence ob tained by this approach, while very >eductive, is frequently suggestive rather than conclusive. Like any other useful concept, metabolite antagonists have defi nite limitations, and these must b e recog nized if the concept is to retain its present usefulness. Application to Chemotherapy As a result of its identification with the sulfa drugs, it is likely that too much was expected in the general application of the metabolite antagonist concept to chemotherapy. Actually there are a num ber of factors which limit the practical usefulness of such subtances. M o s t of these have been pointed out previously (3). Such problems as the toxicity of compounds like neopyrithiamine, and the lack of susceptibility of bacteria n o t re quiring preformed metabolite in t h e case of antagonists of pantothenic acid, biotin, and other metabolites are well recognized. There is also another fundamental diffi culty which is likely to limit seriously the in vivo activity of many antagonists. When an antagonist affects the synthesis of a metabolite, supplying the product of the reaction in the minimal quantity for growth releases its inhibitory action. Since all cells appear to have a great many metabolic processes in common, it is more than likely that the necessary minute amounts of product will b e found in the host cells. As a result very few antagonists which block the utilization of one metabolite in the synthesis of a second are likely t o be effective against bacteria or other parasites in animal tissues containing the second metabolite. If the sulfa drugs act in all cases by interfering with the utilization of p -
3628
aminobenzoic acid in the synthesis o f folic acid, they m a y constitute an e x ception to this conclusion. Actually, o f course, with practically all pathogenic organisms folic acid has no reversing effect on the bacteriostatic action of the sulfanilamides. If this were n o t the case, the concentration of free folic acid in tissues is probably sufficient to prevent completely the antibacterial activity of the sulfa drugs. Regardless of the inter pretation in this instance, it is evident that an exception of this type could overcome the difficulties envisaged in the preceding paragraph. In the field of noninfectious diseases several agents such as the antihistamine and antithyroid compounds, which ap pear to act as specific antagonists, are known and others may be found in the future. Further applications in the treat ment of infections may also be forth coming, although they are likely to b e relatively rare because of the numerous limitations which must be overcome. Any possible antagonists of metabolites required by the parasites but not by the host would be more likely to produce practical results. (Although some of the antibiotics may act as antimetabolites, their actions must be directed against asyet unrecognized metabolites.) Generalizations and Conclusions Attempts to generalize as to what modifications of a metabolite molecule may be expected consistently to produce antagonists are likely to run afoul of results such as those described for oxybiotin in contrast to methoxinine. There are, of course, certain changes which, while not always successful, have been shown to result in antagonists in a number of instances (S). T h e group most often replaced t o produce anti metabolites has probably been the carboxy 1. Sulfonamide and substituted sul fonamide groups, ketones, phosphoric, arsenic, and sulfonic acids replacing a carboxyl group frequently, although not always, result in antagonists. Similarly, replacing one atom b y another in a ring is often successful. Mixed crystal for mation, a related phenomenon, was first utilized to predict that replacement of ring methyl groups with chlorine atoms might lead to antagonists (39). Numer ous other changes, such as one alkyl group for another—for example, ethyl for methyl—and amino for hydroxyl, or vice versa, could also be cited. However, many negative results are never reported, so that one seldom knows how consist ently these changes are successful. Prob ably each new case is a law unto itself and no very general rules for the prepa ration of antimetabolites can be laid down at present. One generalization which has proved to b e quite consistent is that, for o p timum activity, only one change at a time should be made in a metabolite
CHEMICAL
molecule. This observation is illustrated in the following series of compounds related to p-.aminobenzdic acid:
ο ο ο XH2
NH 2
N02
S02NTH2
COOH II NH 2
COOH III N02
I NFH2
G
IN S02NTH2
COOH
0
S0 2 XH 2
I ,IVof course, is sulfanilamide which in V VI volves changing the COOH of p-aminobenzoic acid, II, t o SO2NH2. Similarly, in III and V only one substitution, NOa for Ν Ha, or pyridine for benzene ring, has been made. On t h e other hand, I V and V I involve two simultaneous changes—for instance, SOaNHa for C O O H and pyridine for benzene ring i n I V . Neither of these compounds is known t o possess antibacterial activity in vitro (40, 41), whereas I, III, and V all have a demonstrable bacteriostatic action which is reversible b y p-aminobenzoic acid (3). Similar results have been observed in other series, and it is usually found that more than one simultaneous change in the metabolite molecule is likely t o lead to less potent or entirely inactive antag onists. A s new metabolites are discovered, one may anticipate that the preparation and study of antagonists will become a standard part of any complete biochem ical investigation. I f properly used, metabolite antagonists can help t o u n cover s o m e of the many complex inter relationships which exist in living cells. Because i t has been unusually fruitful in some respects, however, there has been a tendency to overwork the concept b y applying i t in irrelevant situations or without adequate experimental evidence. Unless more rigorous criteria are e m ployed, careless use m a y greatly decrease its value. Occasionally, antimetabolites of prac tical value as chemotherapeutic agents may b e developed, although such cases are likely to be rare. In any event it is a mistake to consider the concept as any royal road to the synthesis of new chemotherapeutic agents. Regardless of this application, it does represent a real step forward in the slow progress toward a better understanding of the relation between chemical structure and biologi cal activity. Literature Cited (1) Fildes, P., Lancet, 1940, I, 955. (2) Woods, D . D., Brit. J. Exptl. Path., 21, 74 (1940). (3) cf. Roblin, R. O., Jr., Chem. Rev., 38, 255 (1946); Woolley, D . W., Physiol. Rev., 27, 308 (1947).
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(4) cf. Haldane, J . B. S., "Enzymes," N e w York, Longmans, Green and Co., 1930. (5) Quastel, J. H., and Wooldridge, W . R., Biochem. J., 22, 689 (1928). (6) cf. Clark, A. J., Heffter's "Handbuch der experintentellen Pharmakologie," Ergânz. 4, Berlin, J. Springer, 1937. (7) Bell, P . H., and Roblin, R. O., Jr., J. Am. Chem. Soc, 64, 2905 (1942). (8) Lampen, J . O., and Jones, M. J., J. Biol. Chem., 166, 435 (1946). (9) Fildes, P., and Rydon, H. N., Brit. J. Exptl. Path., 28, 211 (1947). (10) Rydon, H. N., Ibid., 29, 48 (1948). (11) Dittmer, K., and du Vigneaud, V., Science, 100, 129 (1944). (12) Rogers, L. L., and Shive, W., J. Biol. Chem., 169, 60 (1947). (13) English, J . P., et al, J. Am. Chem. Soc, 67, 295 (1945). (14) Pilgrim, F. J., et al., Science, 102, 35 (1945). (15) Rohlin, R. O., Jr., et al, J. Am. Chem. Soc, 67, 290 (1945). (16) Wilson, A. N., and Harris, S. Α., J. Am. Chem. Soc, 71, 2231 (1949) ; Emerson, G. Α., and Casey, D., private communication. (17) Seeger, D. R., et al, J. Am. Chem. Soc, 69, 2567 (1947). (18) MacLeod, R. Α., and Snell, Ε. Ε., J. Biol Chem., 176, 39 (1948). (19) Ravel, J. M., and Shive, W., Ibid., 166, 407 (1946). (20) Shive, W., and Macow, J., Ibid., 162, 451 (1946). (21) Nielsen, N . , et al, Corny, rend. trav. lab. Carlsberg, Sér. physiol, 24, 39 (1944). (22) Nielsen, N., Naturwissenschaften, 32v 80 (1944). (23) Cheldelin, V. H., and Schink, C. Α., J. Am. Chem. Soc, 69, 2625 (1947). (24) Ivanovics, G., Z. physiol. Chem., 276, 33 (1942); Stansly, P . G., and Alverson, C. M., Science, 103, 398 (1946). (25) Spizizen, J., and Kenney, J. C , Abstr. 3rd Philadelphia Meetingin-Miniature, Jan. 20, 1949, p. 26. (26) Markees, S., Jubilee Vol. Emil Barell, 1946, 406. (27) Vinet, Α., et al, Bull soc. chim. biol., 28, 300 (1946). (28) Snell, E. E., J. Biol Chem., 141, 121 (1941). (29) Winterbottom, R., et al, J. Am. Chem. Soc, 69, 1393 (1947). (30) Woolley, D . W., and Collyer, M. L., J. Biol. Chem., 159, 263 (1945). (31) Woolley, D . W., and Brown, R. Α., Ibid., 163, 481 (1946). (32) Schmidt, L. H., and Sesler, C. L., J. Pharmacol Exptl. Therap., 87, 327 (1946). (33) Browning, C. H., and Gulbransen, R., J. Path. Bact., 25, 395 (1922). (34) Findlay, G. M., "Recent Advances in Chemotherapy," Philadelphia, P. Blakiston's Son & Co., 1939. (35) Hitchings, G. H., et al, J. Biol Chem., 174, 1037 (1948). (36) Rabinowitz, J . C , and Snell, Ε . Ε., Fed. Proc, 8, 240 (1949). (37) Williamson, J., and Lourie, Ε. Μ., Ann. Trop. Med., 40, 255 (1946). (38) Schleyer, W. L., and Schnitzer, R. J., J. Immunol, 60, 265 (1948). (39) Kuhn, R., et al, Ber., 76,1044 (1943). (40) Caldwell, W. T., and Kornfeld, E. C , J. Am. Chem. Soc, 64, 1695 (1942) ; Fellows, E. J., unpublished data. (41) cf. Northey, E . H., "The Sulfonamides and Allied Compounds," New York, Reinhold Publishing Corp., 1948.
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Casey, Authority on Ink Chemistry, Wins Iowa Award Α . τ Atlantic City last September, while more than 8,000 other chemists sweltered in unexpected heat, one man hurried around, busy but comfortable in a white linen suit. T h e wearer was not a particularly astute meteorologist nor a successful crystal gazer, but merely a chemist w h o had learned from long experience that professional meet ings tend to be hot and stuffy affairs. Since Bob Casey came to this conclu sion many years ago his "meeting uni form" of white suit, black bow tie, and black-ribboned glasses has become a familiar sight at scientific meetings throughout the country. Probably most widely known for his work in adapting punch card tech niques to scientific bibliographies, he professes to be "strictly an ink chem ist." However, even h e admits that investigations stimulated b y problems in ink chemistry have on many occa sions led him far from his point of departure. Incongruous as it m a y seem he is co author of a section of I&EC's Materials of Construction review. However, the section is on fibers and Casey's interest in the field derives quite legitimately from studies in connection with the de velopment of washable inks. Robert Casey got into the chemistry of inks early and stayed right with it. In fact if pat phrases were at all ap propriate t o the man he might be called "The Father of Modern Writ ing Ink." After an M.S. from Trinity College and graduate work at Colum bia, he went t o work as the chemist for the W. A. ScheafTer P e n Co., in his native town of Fort Madison, Iowa. Set up with a pine bench and 8100 worth of glassware i n the basement of the plant he was turned loose on the problem of producing an ink that would assure reliable operation in the then newly popularized "fountain" pen. Since, b y his own admission, he knew nothing about ink, he approached the problem as one of matching properties with desired performance. T h e result was Scrip, in production under the management of B o b Casey in 1922. less than two years after h e was hired. Since that time he has progressed in the Scheaffer organization to his pres ent position of director of research, achieved in 1943. H i s work there has resulted not only in improved inks for the company but has helped to make the field of ink chemistry more exact and to eliminate the human factors
» DECEMBER
5,
1949
from the production and testing opera tions. Casey's influence on the adaptation of punched cards to chemical references dates back t o a n article he prepared, together w i t h G. J. Cox and C. F. Bailey, which appeared in C&EN in 1945. This was the first discussion of this technique t o appear i n a major journal and it aroused great interest— Casey answered requests for almost 1,000 reprints. One of Casey's associates says he has a "foolhardy willingness to pitch into any worth-while, but really diffi cult job that comes along." Others who know him would certainly agree and perhaps add that h e displays the same kind of willingness when the prospective enterprise is one of fellow ship or just plain amusement. He plays a wicked hand at the bridge table—except in the hunting season. W h e n the birds start t o fly he makes a second h o m e at a cabin on the Mississippi. Never harrassed, Casey is a master of accepting things as they are. His imperturbability often leads to g e m s of understatement. T h e story is told of a country road on which Casey fell asleep one night while driving. The car took off over a culvert and landed in a dry creek bed, upside down on top of Casey. H e crawled out, walked home, and next morning mentioned casually that a tow truck would have t o b e sent out for his car as he had "run it into the ditch." This incident occurred 30 years ago in his salad days; h e has not fallen asleep at the wheel since, but now, as then, the depart m e n t of understatement still functions. Bob Casey's receipt of the Iowa award for 1949 will b e the second honor which his h o m e state has bestowed on him in recent years ; in 1946 the Iowa Engineering Society named him for the Anson Marston Award for "outstanding contributions t o engineering in Iowa." H e may attain yet another distinction concurrently with the award by the I o w a Section. His family's doctor pre dicts unequivocally that o n Dec. 16, the night of the award dinner, Casey will become a grandfather. B u t if h e does, w e can b e sure that Casey will take i t i n his usual unruffled fashion, laugh, deliver the address, and afterwards drink a toast to his grand child. Monday he will be back at the lab "working his head t o the bone," as h e likes t o put it.
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