摘要:

The culture media from selected fungi grown in submerged culture have been shown to contain enzymes capable of hydrolyzing some synthetic dipeptides and their derivatives. Readily measurable amounts of aminopeptidase, carboxypeptidase, and dipeptidase activity were found, and differences between the systems elaborated by different organisms were observed. The most rapid hydrolysis of N-cbzo-α-L-glutamyl-L-glutamic acid (I) and of N-cbzo-α-L-glutamyl-DL-alanine (II) byGliocladium roseumPRL 86 occurred at pH 4.8 to 4.9. I was hydrolyzed most rapidly byAlternariatenuisPRL 369 at pH 4.7. The activation energies for the hydrolysis of I by PRL 369 and of II by PRL 86 were found to be 11,000 and 15,000 calories per mole, respectively. The activation energy for the hydrolysis of I by PRL 86 was estimated as being between 10,000 and 13,000 calories per mole.

ISSN:0008-4042    

DOI:10.1139/v53-094

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Potentiometric titrations with hydrochloric acid were carried out on standard sodium carbonate solutions containing varying amounts of uranyl nitrate. The results confirmed the fact that uranium is present in such solutions as the complex ion. It was found that only the free CO3−−is titrated with H+up to the first end point at pH = 8. 2. The complex ion is very stable and is decomposed only on further addition of acid when the complexed CO3−−along with the HCO3−in the solution is converted to carbonic acid before the second end point. The pH at which the second end point occurs is lowered from its normal value of 4.0 in the presence of uranium. This effect is attributed to hydrolysis of the UO2++ion. The necessary corrections for determining carbonate and bicarbonate in the presence of uranium are given.

ISSN:0008-4042    

DOI:10.1139/v53-095

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Samples of poly(butadiene-co-styrene) were polymerized in redox systems at 5° and −18 °C., the recipes being such as to yield samples similar in composition, in percentage conversion, and in intrinsic vistex to those prepared at 50°, 40°, 30°, and 15 °C. for an earlier study. The two samples were carefully fractionated and the viscosity functions [η], β, andk′ were determined for each of the fractions,k′ was shown to be the same for all the fractions of a given sample—an indication that there is little or no branching at these low temperatures. Comparison with the earlier results reveals, however, that for unbranched speciesk′ increases as the temperature of polymerization decreases, from 0.327 ± 0.008 at 50° to 0.370 ± 0.005 at −18 °C. This increase ink′ is attributed to an increase in thetrans-1,4-content of the polymer.

ISSN:0008-4042    

DOI:10.1139/v53-096

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

A hitherto unknown minor constituent of the seeds ofAmmivisnagaLam is converted under the influence of 5% alcoholic potassium hydroxide into a compound which seems to be a coumarin. Treatment with methyl-alcoholic alkali yields a substance C15H16O5, whereas treatment with ethyl-alcoholic alkali gives a substance C16H18O5. Dehydrating agents convert both optically active compounds into the same optically inactive dehydration product C14Hl2O4(Substance A). The further investigations carried out with Substance A were: oxidation, after methylation, which yielded α-hydroxyisobutyric acid; fusion with potassium hydroxide, which gave phloroglucinol. On treatment with diluted caustic alkalies two definite products, C10H6O5, probably an acid, and C11H8O4, a ketone, were obtained.

ISSN:0008-4042    

DOI:10.1139/v53-097

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

The virial coefficients of argon have been measured in the temperature and pressure range described. "Best" values of the virial coefficients have been computed from all measurements reported in the literature.

ISSN:0008-4042    

DOI:10.1139/v53-098

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

The difference between adsorption isotherms and absorption spectra of methyl orange bound to human and to bovine albumin at pH 6.8, 9.1, and 11.0 has been studied. Exaltation of the spectrum of methyl orange bound to human albumin is not necessarily correlated with total binding capacity. However, above pH 6.8, heterogeneity of the binding sites for methyl orange on human albumin increases so markedly that it is reflected in an appreciable increase in extinction coefficient for the first three or four anions bound. The exaltation is accompanied by an increased −ΔF° of binding. Increase in ionic strength diminishes exaltation, and denaturation of the protein destroys it. These effects were not observed for bovine albumin. Results are interpreted in terms of a limited reversible expansion of the human protein molecules, without unfolding, due to intramolecular, electrostatic repulsion between groups.

ISSN:0008-4042    

DOI:10.1139/v53-099

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

An original ball-drop impact apparatus has been constructed and used to test the sensitivities of dextrin lead azide and mercury fulminate to mechanical impact. Ball masses and heights were both varied. Both the net kinetic energy and the change of momentum gave continuous functions with the percentage of detonations. Comparisons of the absolute values of the net kinetic energy and the change of momentum with another reported in the literature suggest that momentum is the more important factor in determining the probability of detonation. Values for the momentum at 50% detonations for lead azide and mercury fulminate are 4.6 × 104and 2.6 × 104 c.g.s. units, respectively, with an area of contact of about 0.08 cm2. The corresponding times of impact were found to be about 2.2 × 10−4and 1.9 × 10−4 sec.

ISSN:0008-4042    

DOI:10.1139/v53-100

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

The formation of lignin in wheat plants from C14O2, during the period of rapid lignification, has been studied over the first few hours of photosynthesis by measuring the incorporation of carbon-14 into the guaiacyl and syringyl portions of the lignin molecule. Plants grown 62 days from seeding were exposed to 20 microcuries of C14O2in a closed chamber for 20 min., and grown for periods of 1 to 24 hr. in a normal atmosphere before harvesting. Synthesis of lignin is most rapid four to six hours from activation, the syringyl residues apparently being formed more slowly than the guaiacyl. A slower rate of formation persists for the remainder of a one-day period, probably as a result of recycling in the carbon pool. Cellulose acquires carbon-14 more rapidly than lignin during the period immediately following administration of C14O2, but after three or four hours when synthesis of lignin has become rapid, the total carbon-14 content of both components reaches about the same value.

ISSN:0008-4042    

DOI:10.1139/v53-101

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

On treatment with sodium nitrite, 2-phenylethylamine-1-C14in aqueous hydrochloric, perchloric, acetic, or glacial acetic acid gives rise to products in which the C14atoms have been rearranged from the C-1 to the C-2 position to an extent of 20.5 to 22.5%. The results are discussed on the basis of carbonium ions as possible reaction intermediates.

ISSN:0008-4042    

DOI:10.1139/v53-102

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

not available

ISSN:0008-4042    

DOI:10.1139/v53-103

出版商:NRC Research Press    

年代:1953

数据来源: NRC