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Biomedical subjects

C M Dobson

Publications and source records attributed to C M Dobson.

At least 253 records · Page 14Linked to original sources
PubMed1981

Efficient incorporation of deuterated amino acids into quail egg white proteins for nuclear magnetic resonance studies.

The in vivo incorporation of deuterated amino acids into egg white proteins of Japanese quail is described. Using a synthetic diet, the level of incorporation of selectively deuterated tyrosine, tryptophan, histidine, and phenylalanine into lysozyme was greater than 80% as demonstrated by proton NMR. Load and load-chase experiments using [3H]phenylalanine or [3H]leucine monitored the fast uptake time (t 1/2 = 2 days) and confirmed the high levels of incorporation. The potential of this system for preparation of other proteins for NMR spectroscopy is discussed.

Amino Acids↗
PubMed1980

A conformational isomer of bovine pancreatic trypsin inhibitor protein produced by refolding.

Refolding of the bovine pancreatic trypsin inhibitor protein (BPTI) after reduction of its three cysteine disulphide linkages can occur when the reduced protein is placed in a suitable oxidizing medium (ref. 1 and refs therein). The refolding process has been studied by trapping chemically intermediates which contain only one or two disulphide bonds (ref. 1 and refs therein). We report here that during structural studies of these intermediates by NMR, we have found that complete re-oxidation of the protein results in substantial quantities of a metastable folded species which is identical to native BPTI in its covalent bonding (including the disulphide bonds) but possesses a somewhat different conformation. The existence of such a species is supported by circular dichroism measurements on refolded BPTI. This novel form of BPTI is of considerable interest because it can be used to provide information about the folding mechanism and conformational stability of the protein.

Animals↗
PubMed1980

Nuclear magnetic resonance studies of blood platelets.

Blood platelets contain membrane-enclosed granules which have inside them high concentrations of 5-hydroxytryptamine (serotonin) along with adenine nucleotides and divalent metal ions. 19F n.m.r. of fluorinated serotonin incorporated into the granules of both human and pig intact platelets has shown that the motional state of the serotonin is restricted. Comparison with 31P n.m.r. experiments indicates that this restriction of motion is a consequence of high molecular weight aggregates formed by the adenine nucleotides and metal ions, and that it varies with the species from which the platelets are obtained. In the case of human platelet granules, at least, these high molecular weight aggregates are present in the absence as well as in the presence of serotonin. The biological significance of these data is briefly discussed.

Adenine Nucleotides↗
PubMed1980

A structural study of the hydrophobic box region of lysozyme in solution using nuclear Overhauser effects.

Saturation of specific proton nuclear magnetic resonance (NMR) signals from residues in the hydrophobic box region of lysozyme (EC 3.2.1.17) has enabled negative nuclear Overhauser effects to be measured on the resonances of nearby protons. The assignments of resonances reported previously have been examined, and most have been confirmed. In conjunction with spin-decoupling methods, new assignments could be made so that assignments for some 70 resonances of 25 residues in lysozyme are now known. A high correlation was observed between the observed nuclear Overhauser effects and interproton distances calculated from cyrystallographic data. This indicates that the average structure of this region of lysozyme in the crystalline state is maintained in solution, that substantial populations of structures very different from this do not exist, and that the nuclear Overhauser technique can be applied in a straightforward manner to obtain structural data in solution at the 1-A level.

Amino Acids↗
PubMed1979

Conformational studies on muscular parvalbumins cooperative binding of calcium (II) to parvalbumins.

1H NMR and ORD were used to characterize the respective variations of tertiary structure and secondary structure of parvalbumins with calcium content ((Pa(O), without calcium and PaCa2 calcium saturated) and temperature. It has been observed that the tertiary structure can be lost without significant variation of the helical content. Cooperative binding of calcium to Pa(O) has been shown by NMR spectroscopy under low ionic strength conditions and at neutral pH. The present study shows that the calcium binding affinity of parvalbumin is dependent on the tertiary structure. Calcium binding and calcium release functions of parvalbumins in the muscle may be controlled by their tertiary structure.

Animals↗
PubMed1978

Study of the tryptophan residues of lysozyme using 1H nuclear magnetic resonance.

The identification and complete assignment of the C-2 and N-1 proton nuclear magnetic resonances (NMR) of the six tryptophan residues of hen lysozyme are reported. Identification of the resonances required a detailed examination of the spectra of the protein in H2O and in 2H2O, and involved the application of spin-echo and Carr-Purcell-Meiboom-Gill pulse sequences. Assignment was achieved by observing the effects on the NMR spectra of performing specific chemical modifications, of binding paramagnetic species (lanthanide ions and spin labels), of binding inhibitors and protons and of carrying out solvent exchange experiments. The problems involved in completion of assignment are fully discussed. In the course of performing experiments to make assignments, several interesting aspects of the behaviour of the tryptophan residues in the protein structure were observed and are discussed.

Acetylglucosamine↗
PubMed1978

Complete assignment of aromatic 1H nuclear magnetic resonances of the tyrosine residues of hen lysozyme.

The complete assignment of the aromatic proton nuclear magnetic resonances of the three tyrosine residues in hen lysozyme is reported. These assignments were made using double resonance techniques, specific chemical modifications of one residue (Tyr-23), and by interpretation of the effects of paramagnetic lanthanide ions. Some aspects of the behaviour of the tyrosine residues are reported, including pK values, reactivity towards modifying agents and conformational mobility.

4-Chloro-7-nitrobenzofurazan↗
PubMed1978

Nuclear-magnetic-resonance studies of 5'-ribonucleotide and 5'-deoxyribonucleotide conformations in solution using the lanthanide probe method.

The conformations of the metal-bound 5'-ribonucleotides and 5'-deoxyribonucleotides in aqueous solution at different pH values have been studied using the lanthanide probe method. The conformational analysis, based on mixing different conformations in fast exchange within the nuclear magnetic resonance time scale, agrees well with the results from coupling constants, nuclear Over-hauser effects and spin-lattice relaxation times, obtained for the metal-fixed systems. The equilibrium between the two basic conformational combinations for the 5'-nucleotides, anti-(N in equalibrium S)-gg-g'g' and syn-(N in equalibrium S)-gt-g'g' depends on the nature of the furanose ring, the base and also on the state of base protonation and phosphate ionization. The effect of base protonation is particularly strong for the guanine nucleotides.

Adenosine Monophosphate↗
PubMed1977

Physical and chemical properties of lysozyme.

The conformations of lysozyme in crystals and in aqueous solution are discussed and it is shown that the basic conformation is similar in the two states. Certain parts of the molecule have mobility. The reactions of lysozyme with protons, metal ions and some organic reagents are examined in the light of the conformations and their dynamics. The reactions considered are mainly those of tyrosyl, tryptophyl and carboxylate residues. The reactivity data are used in a discussion of the energy states of the reacting side-chains. In particular the reactivity of Glu-35 and its interaction with Trp-108 lead to suggestions for some new aspects in the hypothesis for the mechanism of action of lysozyme. In most respects the X-ray crystal diffraction and the nuclear magnetic resonance solution studies are in accord and complementary.

Amino Acid Sequence↗