Showing papers in "Biochemical Journal in 1946"

The spectrophotometric determination of tyrosine and tryptophan in proteins.

Abstract: (All right. re8erved) PAGE Protocatechuic acid, the substance responsible for the hardening of the cockroach ootheca. By M. G. M. PRYOR, P. B. RUSSELL and A. R. TODD . . . . . . . . . . . . 627 The spectrophotometric determination of tyrosine and tryptophan in proteins. By T. W. GOODwn and R. A. MORTON . . . . . . . . . . . . . . . . . 628 The estimation of threonine and serine in proteins. By M. W. REES. (With two figures) . . . . 632 Tetryl dermatitis. *2. The interaction of aromatic mitro-compounds with amino-acids and proteins. By I. A. BROWNLIE and W. M. CUMMNG. (With six figures) . . . . . . . . . 640 A modification of the fluorimetric method of determining riboflavin in biological materials. By E. C. SLATER and D. B. MORELL. (With two figures) . . . . . . . . . . . . 644 The fluorimetric determination ofriboflavin in urine. By D. B. MORELL and E. C. SLATER . . . . 652 Carotenoid pigments ofBadami mango fruit. By G. B. RAMAsARMA, S. D. RAO and D. N. HAIM . . . 657 Porphyrin metabolism in yeast. By J. E. KENCH and J. F. WILKSON . . . . . . . 660 The fatty acid and glyceride structures of Indian buffalo milk and depot fats, and some characteristics of eastern animal fats. By K. T. ACHAYA and B. N. BANERJEE. (With one figure). . . . 664 Indigoid pigments derived from a pathological urine. By C. RMINGTTON. With an addendum on 'The spectral absorption of the pigments' by E. R. HOLIDAY and E. M. JOPE. (With six figures) . . . . 669 Combination between different protpins and between proteins and yeast nucleic acid. By A. KLECZKOWSKI. (With one figure) . . . . . . . . . . . . . . . . . 677 The determination and isolation of the organic acids in fruit. By F. A. ISHERWOOD. (With four figures) . 688 The fixation and retention of ascorbic acid by the guinea-pig. By J. R. PENNEY and S. S. ZILVA. (With four figures) . . . . . . . . . . . . . . . . . . 695 Spectrophotometric study of the excretion products of mepacrine compared with synthetic acridine and diph.enylamine derivatives. By E. J. KING, M. GILCHST and A. L. TURNOKY. (With five figures) . 706 Observations upon the application of partition chromatography to the determinationof the monoamino-acids in proteins. By G. R. TRISTRAM. (With three diagrams) . . . . . . . . . 721 Studies on mustard gas(,Bp'-dichlorodiethyl sulphide) and some related compounds. 1. General introduction and acknowledgements. By T. E. BANKS, J. C. BOUrRSNELL, G. E. FRANCIS, F. L. HoPwoOD and A. WORMALL . . . . . . . . . . . . . . . . . 734

The estimation of threonine and serine in proteins

Abstract: 1. The ultra-violet absorption spectra of tyrosine and tryptophan have been determined in 0 1 NNaOH and the curves found to intersect at 257*15 and 294-4 m,u (E, 2748 and 2375, respectively). 2. By using intensities of absorption at 2944and 280 m,, determined by means of a photoelectric spectrophotometer, mixtures of tyrosine and tryptophan may be analyzed with considerable accuracy provided the molar ratios are not greater than 20:1 either way. 3. Using about 25 mg. of material, proteins may be analyzed with comparable accuracy if due correction is made for irrelevant continuous absorption.

The effect of substrate concentration, pH and other factors upon the activity of carbonic anhydrase

Abstract: calculating the extra rate in this unit at a series of instants during the course of the manometric experiment. These extra rates are then extrapolated to zero time so as to eliminate changes in the activity of the enzyme during the actual experiment owing to (i) progressive alterations in pH, substrate and buffer concentrations as C02 is taken up or evolved, (ii) destruction brought about bytheviolent shaking. The extrapolated rates are finally corrected for the limiting effect of diffusion by means of extensions of the equations previously developed by Roughton, on the basis of the application of the stationary film theory to gas-enzymic reactions. 3. Detailed examples of the computation of enzymic activity are given for CO2 uptake experiments both below and above pH 8-0 and also for C02 output experiments. 4. Applications of the methods to the study of the kinetics of carbonic anhydrase under varied conditions are given in the following paper.

The solubilization of polycyclic aromatic hydrocarbons by purines.

Abstract: In all but two cases agreement between the results by the two methods was highly satisfactory, having regard to the nature of the materiaf analyzed. Moreover, such diiferences as existed were not all in one direction, so that there is no indication that one method offers a more efficient method of fat extraction than the other. The two specimens which showed less satisfactory agreement were very watery specimens. Frequently such specimens contain material which separates out from the rest very readily, so that it is hardly possible to maintain uniformity. of composition sufficiently long to weigh out the separate portions required for analysis by the two methods. Differences in the figures in such cases are more likely to represent -a difference in the composition of the material analyzed than a disagreement between the two methods. In no case (including the two specimens just referred to) was there any difference in clinical significance between the figures by the two methods; The plaster method as described gives, therefore, substantially the same results as the wet extraction

On phytic acid, its importance in metabolism and its enzymic cleavage in bread supplemented with calcium

Abstract: Phytic acid, a hexaphosphoric ester of inositol, is found in all plant seeds examined, in grains as well as in oilseeds, and undoubtedly represents a store of phosphoric acid that is hydrolyzed in sprouting. For this reason green plants never contain considerable amounts of phytic acid. The cleavage in the seed is evidently caused by a specific enzyme called phytase, but other phosphatases from plant tissue are able to split the substance to some degree. In most cases no phytase activity is found in resting seeds. The enzyme seems to be formed during sprouting of the seeds. Wheat and rye, and to a certain extent barley and buckwheat, are, however, exceptions from this rule. If the whole flour of these grains is suspended in a buffer solution at pH 5 and left at a temperature of 400 for 2 hr. all the phytic acid in wheat and rye, and a considerable part of the acid in barley and buckwheat, is split into inositol and free phosphoric acid. In flours of any other seeds examined no cleavage of phytic acid takes place under these conditions. Experiments with pure phytase preparations have proved the conditions mentioned to be optimal, and confirm the conclusion that these grains do not contain phytase. Table 1 shows the results of investigations by Pedersen (1940) in M0llgaard's laboratory. Total P was in the experiments of Pedersen and in other experiments referred to in this paper determined by destruction of the substance with concentrated sulphuric' and nitric acids and precipitation as ammonium phosphomolybdate; this was heated at 5500 to form phosphomolybdic acid (Hansen & Grasholm, 1935). The phytic P was determined by extraction with 0-5N-HCI and precipitation as iron phytate; this was decomposed with NaOH, and the P in the dissolved sodium phytate was determined according to the method for total P (Pedersen, 1940). Ca was determined by destruction with concentrated sulphuric acid, dissolution of the ash in diluted hydrochloric acid and precipitation as oxalate, which was titrated with permanganate (Hansen & Graesholm, 1935). Wheat Wheat bran

The free amino group of gramicidin S.

Abstract: on the other hand, maintain that both amino and carboxyl groups are present and that the 8-amino group of the ornithine residue is not free. Their evidence for this latter point, nevertheless, is not very convincing and the problem was clearly one which could be readily settled by applying the new dinitrofluorobenzene (DNFB) method (Sanger, 1945). Accordingly at Dr Synge's suggestion, the present author has made appropriate experiments, which show that the free amino group is undoubtedly the 8-amino group of the ornithine residue. The finding provides additional support for Synge's contention that gramicidin S is a cyclopeptide composed of the five amino-acids linked through their cx-amino and carboxyl groups. It is interesting to note that similar results for tyrocidin have recently been obtained by Christensen (1945) using a different technique. EXPERIMENTAL