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M P Russell

Publications and source records attributed to M P Russell.

17 recordsLinked to original sources
PubMed1996

Structure, interactions and dynamics of PRD1 virus I. Coupling of subunit folding and capsid assembly.

Bacteriophage PRD1, which infects Escherichia coli and Salmonella typhimurium, consists of an icosahedral capsid enclosing a membrane-packaged double-stranded DNA genome. The viral shell has been investigated using time and temperature resolved Raman and ultraviolet-resonance Raman spectroscopy to reveal novel features of the capsid structure and its pathway of assembly from P3 subunits. Raman spectra show that the shell is thermostable to 50 degrees C, and disassembles between 50 and 70 C degrees with only a small change in P3 conformation. However, the products of thermal disassembly depend sensitively upon total protein concentration. Characterization by analytical ultracentrifugation indicates that below 8 mg/ml, the purified shell disassembles primarily into P3 trimers; at higher concentrations, larger multimers of P3 are formed. Guanidine hydrochloride (GuHCl) dissociation of the P3 shell yields similar results. Purified P3 trimers, isolated either by heat or GuHCl treatment, exhibit structure sensitivity between 30 and 50 degrees C. Thus, shell disassembly diminishes P3 thermostability. Both the lower temperature transition (30 degrees C to 50 degrees C) of the trimer and the higher temperature transition (50 degrees C to 70 degrees C) of the shell involve a conversion of approximately 5% of the P3 peptide backbone from alpha-helix to beta-strand. Deuterium exchange of the P3 peptide backbone reveals more rapid exchange in the shell than in the trimer, consistent with the observed non-specific polymerization of trimers at high concentration. Conversely, the exchange of indole 1NH groups shows that approximately 65% of tryptophan residues are protected against exchange in the assembled shell. The results suggest a mechanism for shell assembly in which the specific association of trimers into the correct shell architecture involves stabilization of a subunit alpha-helical domain and sequestering of selected side-chains from solvent access. We propose a capsid assembly model which couples P3 shell formation with the final step in folding of the P3 subunit.

Bacteriophages↗
PubMed1995

Design and performance of an ultraviolet resonance Raman spectrometer for proteins and nucleic acids.

We describe an ultraviolet resonance Raman (UVRR) spectrometer appropriate for structural studies of biological macromolecules and their assemblies. Instrument design includes the following features: a continuous wave, intracavity doubled, ultraviolet laser source for excitation of the Raman spectrum; a rotating cell (or jet source) for presentation of the sample to the laser beam; a Cassegrain optic with f/1.0 aperture for collection of the Raman scattering; a quartz prism dispersing element for rejection of stray light and Rayleigh scattering; a 0.75-m single grating monochromator for dispersion of the Raman scattering; and a liquid-nitrogen-cooled, charge-coupled device for detection of the Raman photons. The performance of this instrument, assessed on the basis of the observed signal-to-noise ratios, the apparent resolution of closely spaced spectral bands, and the wide spectrometer bandpass of 2200 cm-1, is believed superior to previously described UVRR spectrometers of similar design. Performance characteristics of the instrument are demonstrated in UVRR spectra obtained from standard solvents, p-ethylphenol, which serves as a model for the tyrosine side chain, the DNA nucleotide deoxyguanosine-5'-monophosphate, and the human tumor necrosis factor binding protein, which is considered representative of soluble globular proteins.

Acetonitriles↗
PubMed1991

Prognostic significance of carcinoembryonic antigen in colorectal carcinoma. Serum levels before and after resection and before recurrence.

The use of carcinoembryonic antigen was evaluated in 425 patients with a mean follow-up of 48 months. The preoperative and postoperative carcinoembryonic antigen levels were predictive of recurrence and survival independent of the tumor stage. In a multivariate regression analysis of age, location, tumor stage, and preoperative and postoperative carcinoembryonic antigen levels, the latter three factors were significant prognostic variables with respect to the adjusted survival. Recurrent disease was found in 42% of patients, excluding patients with stage IV disease. The carcinoembryonic antigen level at recurrence was greater than 5 ng/mL in 79% of the patients and in 89% of the intra-abdominal recurrences. Carcinoembryonic antigen level at recurrence was not predictive of postrecurrence survival except in the subgroup of locoregional disease. The life span in patients with liver and lung metastases was not influenced by carcinoembryonic antigen level at recurrence. Preoperative and postoperative carcinoembryonic antigen levels can indicate a poorer prognostic group of patients with colorectal cancer who may benefit from adjuvant treatment. The carcinoembryonic antigen at recurrence can be used effectively to diagnose intra-abdominal recurrences and project survival after development of local/regional disease.

Aged↗
PubMed1990

When is polypectomy sufficient treatment for colorectal cancer in a polyp?

Eighty-seven patients with a carcinoma in a polyp were reviewed over a 12-year period. Ten histologic criteria were analyzed for an association with the presence of residual carcinoma. Four factors were identified as having prognostic value: size greater than 1.5 cm, sessility, cancer of at least 50% of the adenoma volume, and invasive carcinoma. Polypectomy alone is adequate treatment unless the carcinoma invades deeper to the muscularis mucosa and is associated with one or more of these characteristics.

Aged↗
PubMed1984

Some factors affecting the efficiency of settle plates.

An evaluation has been made of some of the factors which may affect the efficiency of settle plates. Water loss was found to be linear with time. Although the count was reduced over an 8 h period the reduction was not statistically significant. No difference in total bacterial counts could be detected between four, 1/2 h exposures and one, 2 h exposure. The addition of water and the surface area of the plates had no effect on the total count.

Agar↗
PubMed1983

A comparison of the structure and activity of cat and trout muscle pyruvate kinases.

Pyruvate kinase was purified from cat and trout muscle. The enzymes had similar amino acid compositions and subunit molecular weights. In contrast to the mammalian enzyme, the trout muscle pyruvate kinase was activated by fructose 1,6-bisphosphate. However, unlike the L-type pyruvate kinase from mammalian liver it was not phosphorylated by cyclic-AMP-dependent protein kinase. The purified enzyme from cat muscle was carboxymethylated with iodo[2-14C]acetic acid under conditions that led to the preferential labelling of one especially reactive thiol group. The labelled enzyme was cleaved with CNBr, and the radioactive fragment purified. Amino acid sequence analysis of the reactive-thiol-containing fragment from cat muscle pyruvate kinase showed it had the following sequence: Ile-Gly-Arg-[14C]CmCys-Asn-Arg-Ala-Gly-Lys-Pro-Val-Ile-CmCys-Ala-Thr-Gln- Hse. The corresponding peptide from trout pyruvate kinase had only one difference in its amino acid composition and the sequence around the reactive thiol was identical.

Amino Acids↗
PubMed1981

Ring-hydroxylated propranolol: synthesis and beta-receptor antagonist and vasodilating activities of the seven isomers.

Propranolol (Inderal; 1) is extensively metabolized in man. Metabolites of interest pharmacologically include ring-hydroxylated propranolols (1a-g). In order to identify these ring-oxidized products and to study the effect of hydroxyl position on biological activity, we have synthesized all seven isomers. With the exception of 1b and 1g, the desired compounds were prepared by alkylation of the respective methoxy-1-naphthols with epichlorohydrin and reaction of the resulting epoxide with isopropylamine. Cleavage og the methyl group in fused pyridine hydrochloride afforded 1a,c-f. 1g was prepared by the direct alkylation of 1,8-naphthalenediol (17) with epichlorohydrin, followed by reaction with isopropylamine. 1b was synthesized by treating 2-naphthol (9) with chlorine gas and then treating the resulting 1,1-dichloronaphthalen-2(1H)-one (10) with sodium allyl oxide. Acetylation of the hydroxy function and epoxidatrion of the allyl group, followed by relation with isopropylamine, gave 3'-hydroxy-4'-chloropropranolol (15). Dechlorination gave 1b. All of the racemic hydroxylated propranolols produced beta blockade and direct vasodilation in anesthetized dogs. The potency is strongly dependent upon the position of the hydroxyl group, i.e., 1e is 4 times as potent as 1 as a beta receptor antagonist, whereas 1a, 1b, and 1g are all significantly less potent than 1. For direct vasodilation, 1a and 1g are equipotent to 1, while 1b-f are much less potent. The potencies of the compounds were also compared with their 1-octanol/pH 7.4 buffer distribution coefficients; the direct vasodilating potency was found to increase with increasing lipophilicity, while the beta-adrenergic antagonist potency decreased.

Adrenergic beta-Antagonists↗
PubMed1980

The gamma-aminobutyrate content of nerve endings (synaptosomes) in mice after the intramuscular injection of gamma-aminobutyrate-elevating agents: a possible role in anticonvulsant activity.

The intramuscular administration of L-cycloserine, gabaculine, and aminooxyacetic acid caused significant, time-dependent increases in the gamma-aminobutyric acid (GABA) content of both whole brain and synaptosomal-enriched preparations obtained from the tissue, a linear relationship being observed between the two parameters. In contrast, the administration of hydrazine resulted in a large increase in whole brain GABA level, with little change in the synaptosomal GABA content. The key factor in these different responses appeared to be the degree of inhibition of glutamic acid decarboxylase by the drugs. Pretreatment of mice with the GABA-elevating agents resulted in a delay in the onset of seizures, which was related directly to the increase in synaptosomal GABA content. Although the seizures were delayed, they occurred while the GABA content of nerve endings (synaptosomes) was above that in preparations from untreated animals. The decrease in GABA content at the onset of seizures, expressed as a percentage of the level at the time of injection of the convulsant agent, was, however, reasonably constant. A hypothesis to explain these results is proposed.

Acetates↗