Ultraviolet Spectral Properties Research Articles

The Trypsin-catalyzed Hydrolysis of Nα-Benzyloxycarbonyl-l-Lysine p-Nitrophenyl Ester in Dimethylsulfoxide at Sub-Zero Temperatures

Abstract The effect of sub-zero temperatures and aqueous dimethylsulfoxide solutions on the trypsin-catalyzed hydrolysis of Nα-benzyloxycarbonyl-l-lysine p-nitrophenyl ester has been investigated. With increasing dimethylsulfoxide concentration at 0°, kcat decreases in proportion to the decreased water concentration; however, Km increases by 2 orders of magnitude. The effect on Km can be accounted for by a combination of dielectric and competitive inhibition effects. The Arrhenius plot for the deacylation reaction in 65 % aqueous dimethylsulfoxide is linear over the range 0 to -45° and extrapolates to a value of kcat at 25° in excellent agreement with that obtained in the absence of the organic solvent. At -45° and below, turnover occurred very slowly, but acylation was quite rapid. The effect of dimethylsulfoxide concentration and sub-zero temperatures on the ultraviolet spectral properties of the enzyme showed no evidence of any structural changes. All of the experimental observations were consistent with the conclusion that 65 % aqueous dimethylsulfoxide and sub-zero temperatures have no significant effect on the pathway of trypsin-catalyzed reactions. Preliminary results using Nα-acetyl-l-lysine methyl ester indicated that detectable perturbations in the environment of tyrosine and tryptophan residues in trypsin occur during catalysis.

Ultraviolet spectral properties of protonated amides; the question of the site of protonation

Acidity dependent changes in the π–π* and n–π* absorption bands of aliphatic amides indicate that the N-protonated species constitutes no more than a very small fraction (ca. 10–3) of the total protonated amide.

Synthesis of two new heterocyclic ring systems: Benzo[3,4] cyclohepta[1,2‐d]‐pyrimidines and benzo[3,4]cyclohepta[2,1‐d] pyrimidines

AbstractThree 2,4‐diamino‐l(), 11‐dihydro‐9H‐benzo[3,4]cyclohepta[ 1,2‐d]pyrimidines (6a‐6c) representing the first examples of a new ring system were synthesized from 2‐benzosuberones and cyanoguanidine. Similarly, 2,4‐diamino‐6,7‐dihydro‐5H‐benzo[3,4]cyelohepta[2,1‐d]pyrimidine (24) was prepared from 1‐benzosuberone. The ultraviolet spectral properties of these compounds were examined with reference to those of the analogs in which the central ring is five‐ and six‐mernbered.

Synthe´se et comportement d'α silyl ce´tones cycliques

Several cyclic α-silyl ketones have been synthesized from 2,2-diphenyl-1,2,3,4-tetrahhdro-2-silanaphthalene and some homologous compounds. Their infrared and ultraviolet spectral properties have been determined. Their chemical behaviour has been examined, especially the coupling with Grignard reagents. These reagents react without decomposition of the ketone and give addition or reduction products.

Eight coordinate tetrakis-chelate complexes of niobium(IV) and tantalum(IV)

Eight coordinate complexes of the NbIV(chelate)4 have been obtained by the reaciton of niobium tetrachloride with troplone, 8 hydorxyquinoline, and a number of β-diketones, in the presence of base. In the presence of dioxane. the acetylacetonate complex forms NbIV(acac)4(dioxane) which is probably nine coordinate. Chlorine-containing products of the type NbIVClz(CHELATE)2 and NbIVCl(chelate)3 were obtained in the absence of base. Similar reactions were studied with tantalum tetrachloride, but these were complicated by oxygen-abstraction reactions forming for example [TaVCl3(chelate)]2O. The tetrakis chelate complexes are the first eight coordinate d1 complexes of this type to be reported, and the magnetic and ultra violet and visible spectral properties are discussed.

Infrared, nuclear magnetic, and ultraviolet spectral and gas chromatographic properties of some aromatic acid trimethylsilyl derivatives

Summary Infrared, nuclear magnetic resonance, and ultraviolet spectral data fortrimethylsilyl derivatives of aromatic acids that might be found in biological samples have been presented. Gas chromatographic retentions in the form of methylene units have also been given. In addition to enabling the investigator to identify a specific compound, the spectra and methylene unit information suggest generalizations correlating functional groups with specific spectral or gas chromatographic properties. The latter information could be helpful in determining the structure of a compound isolated from a biological sample for which no spectral or gas chromatographic properties have been published.

Specificity of the three-stranded complex formation between double-stranded DNA and single-stranded RNA containing repeating nucleotide sequences

Three-stranded nucleic acid complexes have been shown to be formed from double-stranded DNA and single-stranded RNA polymers with restricted base sequences. Complex formation takes place only when the DNA contains all purine bases in one strand and all pyrimidine bases in the other strand and the RNA must be a polypyrimidine polymer. Hence, poly (dA)·(dT) forms a three-stranded complex with poly U, and poly d(T-C)·d(G-A) † † Abbreviations for the polynucleotides used in this study are those given in the Revised Tentative Rules (1965) of IUPAC-IUB in J. Biol. Chem. (1966) 241, 527. The abbreviation CH + indicates the protonated form of cytidylic acid. forms a three-stranded complex with poly (U-C) in acidic solutions. No other RNA's including the random co-polymer poly (U,C) interact with poly d(T-C)·dG-A) to give a stoichiometric three-stranded structure. Under no condition is a complex detected between poly d(T-G)·d(C-A) or poly d(A-T)·d(A-T) and any polyribonucleotide. The three-stranded poly d(T-C)·d(G-A)·(U-CH +) was characterized by cesium sulfate buoyant density studies, by continuous variations study, by ultraviolet spectral properties and by optical density-temperature profiles. Addition of poly (U-C) to poly d(T-C)·d(G-A) and addition of poly U to poly (dA)·(dT), prior to the addition of Escherichia coli RNA polymerase, effectively reduced the transcription rate of both strands of these DNA's. Other combinations of RNA's with DNA's showed essentially no inhibition; all of these RNA-DNA mixtures were also found to be inert as regards triplex formation. Possible biological roles of the triplexes are discussed.

The effect of heat on the ultraviolet spectral properties of tobacco mosaic virus ribonucleic acid complexed with Hg(II).

Abstract 1. 1. The Amax of TMV-RNA complexed with Hg(II) at different molar ratios (r) of Hg(II) per nucleotide at 0 ≤ r ≤ 10.0 was determined as a function of temperature between 25° and 90–95°. 2. 2. The resulting hyperchromicity of the Amax from heating decreased with increasing values of r for 0.25 ≤ r ≤ 1.0. 3. 3. Heating resulted in an initial hypochromicity of the Amax at 0.90 ≤ r ≤ 10.0. This was followed by hyperchromicity as the temperature was raised further. 4. 4. The wavelength of the Amax shortened with increasing temperature at 0.25 ≤ r ≤ 1.0, the amount of shift increasing with increasing values of r. 5. 5. At r = 10.0, the change in chromicity of the Amax from heating was relatively slight and no shift in the wavelength took place under these conditions. 6. 6. These results are interpreted as a heat-induced reversal of the chromicity changes and bathychromic shift of the Amax that takes place as a result of increasing r at room temperature and hence are explained here as a heat-induced dissociation of the Hg(II) from the TMV-RNA. 7. 7. The amount of change in chromicity of the Amax or change in the wavelength shift of the Amax per increment of Hg(II), both at room temperature and under conditions of heating, shows a biphasic distribution with a sharp break in all cases at 0.50 ≤ r ≤ 0.75. Increments of Hg(II) at 1.0 ≤ r ≤ 10.0 have little effect. 8. 8. This biphasic set of reactions is interpreted as the formation of two types of complexes, one, a base-Hg-base, intramolecular, cross-linked, compact structure for 0 , and the other, a single-base-Hg, extended structure for 0.50 with the limit of the latter reaction set at one Hg(II) per nucleotide.

OPTICAL ROTATORY AND ULTRAVIOLET SPECTRAL PROPERTIES OF BENCE-JONES PROTEINS.

OPTICAL ROTATORY AND ULTRAVIOLET SPECTRAL PROPERTIES OF BENCE-JONES PROTEINS.

Structure of Muramidase (Lysozynie)

In order to obtain information on the factors which stabilize the internal fold of the muramidase molecule, the effects of methanol, isopropanol, n-propanol, glycerol, α monochlorohydrin and ethylene glycol monomethyl ether on the optical rotatory and ultraviolet spectral properties have been studied. The following observations have been made: The effectiveness to disrupt the internal fold of the muramidase molecule increases with both chain length and increasing the hydrocarbon content.On the other hand, increasing the hydroxyl content of the solvent molecule had no significant effect on the internal fold. Thus, ethylene glycol and glycerol disrupt neither the internal fold nor the helical part.These observations suggest that the internal fold of the muramidase molecule is stabilized by hydrophobic forces.While there is no evidence for an increase in the helical Content of the muramidase molecule in the presence of methanol or ethanol, isopropanol and n-propanol increase the helical content.An increase in the helical content of the muramidase molecule was observed it acidic aqueous solutions of methanol, ethanol or isopropanol. The optical rotatory and ultraviolet spectral properties in these solvent are quite similar to those in aqueous 2-chioro ethanol in which hydrochloric acid is present α-Monochlorohydrin which contains hydro chloric acid also increases the helical content Thus, the acidic aqueous solutions of alcohol and the related compounds also can act a helix-former for muramidase. The effectiveness to disrupt the internal fold of the muramidase molecule increases with both chain length and increasing the hydrocarbon content. On the other hand, increasing the hydroxyl content of the solvent molecule had no significant effect on the internal fold. Thus, ethylene glycol and glycerol disrupt neither the internal fold nor the helical part. These observations suggest that the internal fold of the muramidase molecule is stabilized by hydrophobic forces. While there is no evidence for an increase in the helical Content of the muramidase molecule in the presence of methanol or ethanol, isopropanol and n-propanol increase the helical content. An increase in the helical content of the muramidase molecule was observed it acidic aqueous solutions of methanol, ethanol or isopropanol. The optical rotatory and ultraviolet spectral properties in these solvent are quite similar to those in aqueous 2-chioro ethanol in which hydrochloric acid is present α-Monochlorohydrin which contains hydro chloric acid also increases the helical content Thus, the acidic aqueous solutions of alcohol and the related compounds also can act a helix-former for muramidase.

Studies on indolepyruvic acid: II. Ultraviolet spectrophotometry

Indolepyruvic acid in solution shows a pronounced tendency to establish a tautomeric equilibrium. Possessing the enol configuration in its crystalline state, in water-containing solvents it will rapidly convert to the keto tautomer, or degrade along as yet unestablished patterns. These conclusions have been drawn as the result of an extensive investigation of the ultraviolet spectral properties of indolepyruvic acid in relation to the solvents used, and to the different conditions of pH of the medium. In addition, the ultraviolet spectrum of indolepyruvic acid has been compared with that of its methyl ester, indoleacrylic acid, and a number of other indole derivatives. The data obtained from the ultraviolet spectral properties of indolepyruvic acid were found to be in agreement with previous reports on the tautomerism of this compound, and of other aromatic α-keto acids.