Small Amount Of Dimer Research Articles

Purification of thymine dimer from monomer solution in preparative liquid chromatography

Cyclobutane pyrimidine dimers and monomers of thymine were separated on a C18 reversed-phase high performance liquid chromatographic column. Using two mathematical models, the effect of the sample sizes on peak shapes in preparative liquid chromatography was investigated. One of these approaches is through a linear kinetic model, and the other is based on the non-linear adsorption isotherm. With the injection of small samples good agreement between the calculated value by the linear kinetic model and experimental, data were achieved. With increased sample size, this model is defective in its prediction of large concentration profiles of sample. However, the nonlinear model permits the accurate prediction of the location of the component band and the determination of the appropriate time to start and stop collection of the enriched fraction at higher concentrations of monomer and the lower concentrations of dimer. Therefore, extremely small amounts of dimer can be extracted from monomer solutions.

Major lectin of alligator liver is specific for mannose/L-fucose.

We surveyed the calcium-requiring (C-type) lectins in alligator liver. The major lectin purified by affinity chromatography was termed alligator hepatic lectin (AHL) and was found to be specific for mannose/L-fucose. AHL contained approximately equal amounts of 21- and 23-kDa bands upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Binding characteristics of AHL were similar to those of hepatic lectins of other classes in that 1) only terminal monosaccharide was recognized, and 2) the affinity increased exponentially when neoglycoproteins containing increasing numbers of mannose or L-fucose were used as ligand. However, unlike mammalian and chicken hepatic lectins, which exist as hexamers in Triton-containing solutions, AHL was present mainly as monomers, although small amounts of dimer and higher oligomers were present in equilibrium. Mannose-binding proteins and mannose-specific lectins of macrophages bind N-acetylmannosamine, glucose, and N-acetylglucosamine in addition to mannose, indicating that the nature and orientation of the C-2 substituent are not important to these lectins. In contrast, AHL shows a strict requirement for the presence of an axial hydroxyl group at the C-2 position (i.e. mannose).

Kinetics of the thermal degradation of partially para-brominated polystyrenes

The thermal degradation behaviour of various partially para-brominated polystyrenes with increasing ratios of bromostyrene, has been studied by isothermal thermogravimetric analysis in the range 360–410°C, and gas chromatography-mass spectroscopy. The final weight loss was about 95% of the initial sample. The main products, formed in the decomposition are the monomers (styrene and 4-bromostyrene), and small amounts of dimers. The mechanism seems to be the same as for polystyrene. A kinetic model, based on random initiation, depropagation and termination, shows good agreement between experimental and theoretical results. Kinetic parameters of the thermal degradation were calculated and the activation energies shown to decrease as the bromination ratio increases.

Effect of sample sizes on peak shapes in preparative liquid chromatography

Cyclobutane pyrimidine dimers and monomers of thymine were separated on a C18 reversed-phase high performance liquid Chromatographic column. Using the two mathematical models, the effect of the sample sizes on peak shapes in preparative liquid chromatography was investigated. One of them is the linear kinetic model, and the other is based on the nonlinear adsorption isotherm. In case of small injections of sample, the good agreements between the calculated value by the linear kinetic model and experimental data were achieved. However, when sample size is increased, this model lacks in the prediction of large concentration profile of sample. However, the nonlinear model permits the accurate prediction of the location of the component ▪ band and the determination of the appropriate time to start and stop collection of the enriched fraction at the higher concentrations of monomer and the lower that of dimer. Therefore, extremely small amounts of dimer can be extracted from monomer solutions.

Head‐to‐head polymers, 14. Thermal degradation of head‐to‐head and head‐to‐tail polystyrenes and poly(vinylcyclohexane)s

AbstractThe thermal degradation behavior of head‐to‐head (H‐H) and head‐to‐tail (H‐T) polystyrenes and poly(vinylcyclohexane)s has been investigated by direct pyrolysis in a mass spectrometer. Both H‐H and H‐T isomers show only small differences in their initial temperatures of decomposition but remarkably different degradation processes. Whereas H‐T polystyrene decomposes in accordance with earlier investigations mainly by a radicalic depolymerization into the monomer and yields only a small amount of dimer and trimer, the H‐H polystyrene shows no unzipping and only a statistic degradation into oligomeric styrenes. The formation of stilbene is a diagnostic reaction of H‐H polystyrene. The pyrolysis‐mass spectra of H‐H and H‐T poly(vinylcyclohexane)s are more similar than those of the polystyrenes but the favored thermal cleavage between the two tertiary carbon atoms or next to the tertiary carbon atoms of the polymer backbone chain leads to some characteristic fragments, e.g. 1,3‐dicyclohexylpropene from the H‐T and 1,2‐dicyclohexylethane from the H‐H polymer.

Thermal stability of ring-substituted polystyrenes

The thermal stabilities of ring-substituted polystyrenes, containing OMe, Me, Br and Cl para substituents, were investigated using thermogravimetry, gel permeation chromatography and gc/mass spectrometry. Thermal stability of the polymers containing electron repelling groups (OMe. Me) was greater than that of the polymers containing electron withdrawing groups (Br, Cl). These polymers were predominantly depolymerized together with small amount of dimers. The reactivity of depolymerizing radicals was affected by the nature of para substituents. The differing reactivity in addition to weak links, influenced thermal stability.

Photoexchange of η 5-cyclopentadienide ligands in selected systems

Cyclopentadienide ligands are exchanged between molecules of di-η 5 cyclopentadienyltitanium monochloride in benzene, and between bis(methyl-η 5-cyclopentadienyl)vanadium dichloride and di-η 5-cyclopentadienylvanadium dichloride in benzene by a photochemical process. A small amount of dimer is produced upon photolysis of benzene solutions containing both 1,1′-trimethylene titanocene dichloride and titanocene dichloride.

Excision of pyrimidine dimers in normal and T4-infected Escherichia coli: Effect of polA and other mutations

Strains carrying both polA1 and recB ts1 mutations, which are defective in DNA polymerase I and have thermolabile exonuclease V (the recBC enzyme), are viable at 30°C but not at 42°C. These mutants exhibit almost normal rate of dimer excision in vivo even at the restrictive temperature. Similar results were obtained with other polA − strains. We have also investigated effect of host and phage mutations on excision of dimers in T4-infected cells. Only a small amount of dimer is excised in T4v 1- infected cells whereas an extensive and selective release of dimers takes place in T4D-infected cells. Other phage mutations, including mutations in gene 43 and gene 30, do not affect excision of dimers in infected cells.

Antigenicity of Formaldehyde-Inactivated Staphylococcal Enterotoxin B

Abstract The reactivity toward or ability to stimulate production of antibodies specific for native staphylococcal enterotoxin B (nSEB) demonstrated by formaldehyde-inactivated toxin (fSEB) is directly related to the extent to which SEB is polymerized by aqueous formaldehyde. Combined use of polyacrylamide gel electrophoresis in sodium dodecyl sulfate and agarose gel chromatography revealed that: 1) 30-days incubation of SEB in 1% formaldehyde solution buffered to pH 5.0 or 7.5 resulted in a series of small to very large SEB polymers, while SEB incubated at pH 9.5 formed heterogeneous monomers and a small amount of dimer; 2) SEB was polymerized to maximal extent in pH 7.5 formaldehyde. Polymeric fSEB obtained with neutral or acid formaldehyde retained the capacity to precipitate quantitatively nSEB antibodies from rabbit antiserum and to induce the formation of nSEB hemagglutinins in rhesus monkeys. In contrast, the nonpolymerized fSEB failed to react with, or stimulate production of nSEB antibodies. Furthermore, the relative in vitro antibody-combining activities of the two polymeric fSEB products were inversely related to in vivo antibody production. Thus, although quantitative precipitation experiments revealed that 50% of the native antigenic determinants were retained after polymerization in acid aqueous formaldehyde (5.0-fSEB), while only 15% were preserved upon polymerization in neutral formaldehyde solution (7.5-fSEB), hemagglutinin responses of rhesus monkeys were generally several fold greater after parenteral injection of 7.5-fSEB than of 5.0-fSEB. The greater antibody response to 7.5-fSEB may be explained by its more extensive polymerization; the greater average molecular size of the 7.5-fSEB antigenic complex may permit more efficient processing by macrophages or provide a more effective presentation of reactive sites for attachment with, or activation of, immunocompetent cells.

Mechanism of repair of DNA in bacteriophage. I. Excision of pyrimidine dimers from ultraviolet-irradiated DNA by an extract of T4-infected cells.

Abstract When [14C]thymine-labeled T4 DNA, after exposure to ultraviolet light, was incubated with an extract of T4-infected Escherichia coli, pyrimidine dimers were selectively released into the acid-soluble fraction; the rate of release of dimers was about five times greater than that for thymine. The reaction requires Mg2+ and proceeds at pH 7 to 8 in the dark. The amount of thymine and thymine-containing dimers released from the ultraviolet-irradiated DNA into the acid-soluble fraction was determined by Dowex 1 column chromatography. Dimers lost from the DNA were almost quantitatively recovered, in the form of nuoleotides but not of free bases or nucleosides, in the acid-soluble fraction. As a result of the specific release of dimers, the content of dimers in the DNA decreases progressively during the incubation. Thus the excision in vitro is similar to the reaction observed in vivo in ultraviolet-resistant cells. An extract of normal cells does not exhibit the preferential release of dimers even when the homologous E. coli DNA is used as substrate. Only a small amount of dimers is released into the acid-soluble fraction during the incubation of irradiated E. coli or T4 DNA with the normal cell extract. Thus the level of dimer-excising activity of normal cells, if any, must be very low compared with that of T4-infected cells. It is likely that enzyme(s) responsible for excision of dimers is induced by infection with T4.

Two Trypsin Inhibitors from Porcine Pancreatic Juice

Abstract Two trypsin inhibitors of the Kazal type have been isolated from porcine pancreatic juice. They have been prepared in 65% yield by gel filtration on Sephadex G-75 at pH 8.1 in the presence of 10-4 m diisopropyl phosphofluoridate, filtration through diethylaminoethyl cellulose at pH 9, and equilibrium chromatography on sulfoethyl Sephadex at pH 5.4. The major component, Porcine Inhibitor I, has a chemical molecular weight of 6024 and contains 56 residues per molecule: Asp4, Thr6, Ser6, Glu7, Pro5, Gly4, Ala1, Cys6, Val4, Ile3, Leu2, Tyr2, Lys4, Arg2. The minor component, Porcine Inhibitor II, contains 1 residue each fewer of glutamic acid, threonine, serine, and proline. The amino-terminal amino acid sequences, Thr-Ser-Pro-Gln-Arg-Glx-Ala and Arg-Glx-Ala (where Glx denotes glutamyl or glutaninyl), have been determined for Porcine Inhibitors I and II. It is likely that Inhibitor II is equivalent to residues 5 through 56 of Inhibitor I. The inhibitor isolated from bovine pancreatic juice (Greene, L. J., Rigbi, M., and Fackre, D. S., J. Biol. Chem., 241, 5610 (1966)) contains 56 amino acid residues and has the amino-terminal sequence Asn-Ile-Leu-Gly-Arg-Glu-Ala. There are a minimum of eight differences in amino acid sequence when Porcine Inhibitor I is compared with bovine inhibitor. The polypeptides are homogeneous by equilibrium chromatography, electrophoresis, and amino acid analysis, and also on the basis of the stoichiometry of their interaction with trypsin. The preparations appear to contain small amounts of dimer not in rapid equilibrium with monomer. The monomer molecular weights, determined by equilibrium centrifugation, and the minimum molecular weights, determined from the stoichiometry of the interactions with trypsin, are consistent with the chemical molecular weights calculated from amino acid composition. The inhibitors are secreted in the pancreatic juice in the free form (not combined with trypsin) and together are equivalent to 0.1% of the total protein in pancreatic juice. The relative concentrations are 4:1 for Inhibitors I and II, respectively. Burck, Cerwinsky, and Grinnan (Abstracts of the American Chemical Society Meeting, Chicago, September 1967, p. C-22) have prepared a fraction containing both inhibitors from acid extracts of porcine pancreas, and Fritz et al. (Hoppe-Seyler's Z. Physiol. Chem., 348, 405 (1967)) have isolated a porcine inhibitor containing 53 residues of similar composition and properties. A partial purification of prekallikrein was achieved when porcine pancreatic juice was filtered on Sephadex G-75.