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C Fronticelli

Publications and source records attributed to C Fronticelli.

69 records · Page 4Linked to original sources
PubMed1980

Conformational changes in the hemoglobin S system as seen by proton binding.

The proton binding behavior of the carbon monoxy derivatives of hemoglobins A and S, the respective beta-subunits (in the native form and with the cysteines combined with p-mercuribenzoate), and the respective beta (1-55) peptides have been measured. The results show that in the systems obtained from hemoglobin S there is a group which shifts its pK from about 7.0 to 8.35 in the beta-subunits that were reacted with p-mercuribenzoate and to more than 9.0 in the beta (1-55) peptide. Proton nuclear magnetic resonance measurements indicate that in the peptide beta (1-55) from hemoglobin S this residue is the histidine at beta 2. It is proposed that this pK shift is due to the formation of a salt bridge between beta 2 His and beta 7 Glu. This structure would disrupt the first turn of the A helix of the beta s-subunits. Its stabilization by extramolecular contacts may be relevant to the mechanism of fiber formation of hemoglobin S.

Carboxyhemoglobin↗
PubMed1979

Conformation in solution of hemoglobin Osler (alpha 2 A beta 2 145 Tyr replaced by Asp).

Computer simulations of Gelin and Karplus ((1977) Proc. Natl. Acad. Sci. U.S.A. 74, 801-805) suggest that in hemoglobin upon ligation the penultimate tyrosyl residues of the subunits are not expelled from the hydrophobic pockets described in the crystals between the helices E and F (Perutz, M.F. (1970) Nature 228, 726-737). This implies that both the liganded and unliganded conformations of hemoglobin may be affected by mutations involving such residues. Investigation of the conformational behavior of liganded and unliganded hemoglobin Osler was conducted measuring the functional properties, the subunits dissociation, the CD and electronic spectra, the protons absorption upon interaction with polyanions, and the reactivity of the -SH groups of the protein. The results suggest that both the liganded and unliganded conformations of the system are affected by the mutation, confirming the anticipations of Gelin and Karplus on the relevance of tyrosine at beta 145 for both allosteric states of hemoglobin.

Alkylation↗
PubMed1978

Effect of the beta6 Glu replaced by Val mutation on the optical activity of hemoglobin S and of its beta subunits.

The carbomonoxy derivatives of hemoglobin A and S showed a different optical activity in the Soret region of the spectrum as measured by circular dichroism. Different optical activity was also measured in the carbomonoxy derivatives of the beta subunits of hemoglobin A and S, the respective deoxy derivatives showed different circular dichroism spectra only in the presence of inositol hexaphosphate. Sedimentation velocity experiments showed that the differences in optical activity are not due to a different state of aggregation of the subunits. Modification of the tertiary structure of the beta subunits seems to be responsible for the phenomenon. Speculation based on the work of Hsu and Woody (Hsu, M.C., and Woody, R.W. (1971) J. Am. Chem. Soc. 93, 3515-3525) suggests the involvement of the beta15 tryptophan in the conformational changes produced by the beta6 Glu-Val mutation in hemoglobin S.

Carboxyhemoglobin↗
PubMed1976

Conformational relevance of the beta6Glu replaced by Val mutation in the beta subunits and in the beta(1-55) and beta(1-30) peptides of hemoglobin S.

The beta subunits of hemoglobin S showed a higher ellipticity than the beta subunits of the hemoglobin A, both in the Soret and near-ultraviolet regions. The apoderivatives of the beta subunits of hemoglobin S showed a lower helical content and a larger amount of beta conformation than the apoderivatives of the beta subunits of hemoglobin A. The beta(1-55) peptides and beta(1-30) peptides from the beta subunits of hemoglobin A and S have been separated and analyzed. The betaS(1-55) peptide showed a higher content of beta conformation and lower amount of alpha helix when compared to the betaA(1-55) peptide. This difference was present also in different concentrations of methanol. The apoderivative from the beta subunits of hemoglobin S and the betaS(1-55) peptide aggregated with increasing ionic strength. The CD measurement showed that their secondary structure did not change upon a 10-fold dilution of the sample. Very little secondary structure was present in the betaS(1-30) peptide, and the CD spectrum was very similar to that of the betaA(1-30) peptide. No significant difference in aggregation was found between the betaS(1-30) and betaA(1-30) peptides.

Amino Acid Sequence↗
PubMedDate not supplied

[Role of the total and prolonged diversion of portal blood on hepatic function in the rat].

In this experience the effect on hepatic parenchyma and function has been analyzed 180 days after total portacaval shunt. The portacaval shunt induces 50% mortality rate at six months. In the survived animals a significant reduction of hepatic mass has been observed. The liver still presents significant elevation of necrosis and cholestasis enzymes. The residual hepatocellular function related to hepatic mass is comparable to sham operated rats, but it is quite insufficient to maintain endogenous clearances.

Animals↗