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Biomedical subjects

H Crespi

Publications and source records attributed to H Crespi.

9 recordsLinked to original sources
PubMed1992

Domain structure of the human immunodeficiency virus reverse transcriptase.

The spatial arrangement of subunits p51 and p66 of the HIV-1 reverse transcriptase and the position of the RNase H containing domain, p15, have been determined by means of neutron small-angle scattering. The reverse transcriptase (p66/p51) is a flat molecule, which can be approximated by an ellipsoid with the half axes of 5.2 nm, 4.8 nm and 1.4 nm. The two subunits p51 and p66 having a centre-to-centre distance of 3.3 +/- 0.3 nm are attached at their flat sides, slightly shifted sideways. The p15 domain is located at the long axis of the ellipsoidal reverse transcriptase having a distance of 5.0 +/- 0.5 nm to the centre of the p51d domain, which is part of the p66 subunit, and a distance of 5.3 +/- 1.2 nm to the centre of the neighbouring p51s subunit.

Chromatography, Affinity↗
PubMed1989

Changes in the structure of calmodulin induced by a peptide based on the calmodulin-binding domain of myosin light chain kinase.

Small-angle X-ray and neutron scattering data were used to study the solution structure of calmodulin complexed with a synthetic peptide corresponding to residues 577-603 of rabbit skeletal muscle myosin light chain kinase. The X-ray data indicate that, in the presence of Ca2+, the calmodulin-peptide complex has a structure that is considerably more compact than uncomplexed calmodulin. The radius of gyration, Rg, for the complex is approximately 20% smaller than that of uncomplexed Ca2+.calmodulin (16 vs 21 A), and the maximum dimension, dmax, for the complex is also about 20% smaller (49 vs 67 A). The peptide-induced conformational rearrangement of calmodulin is [Ca2+] dependent. The length distribution function for the complex is more symmetric than that for uncomplexed Ca2+.calmodulin, indicating that more of the mass is distributed toward the center of mass for the complex, compared with the dumbell-shaped Ca2+.calmodulin. The solvent contrast dependence of Rg for neutron scattering indicates that the peptide is located more toward the center of the complex, while the calmodulin is located more peripherally, and that the centers of mass of the calmodulin and the peptide are not coincident. The scattering data support the hypothesis that the interconnecting helix region observed in the crystal structure for calmodulin is quite flexible in solution, allowing the two lobes of calmodulin to form close contacts on binding the peptide. This flexibility of the central helix may play a critical role in activating target enzymes such as myosin light chain kinase.

Animals↗
PubMed1988

[Therapeutic use of human leukocyte interferon in dermatologic disorders caused by herpes simplex virus. Multicenter study].

A multi-institutional double blind study was performed in 66 patients in order to evaluate the action of human leukocyte interferon, type alpha (IFN) in lesions produced by herpes simplex virus. Lesions were localized in genital area in 34 cases and in facial area in 32 of them. From the total, 38 patients were treated with 7,000 Ul/gm. of interferon ointment and 28 with carbowax 4,000 as placebo. The symptoms pain, ardor, itching and paresthesia were evaluated asking to patients. Erythema, vesicles, crust, scale adenopathy were objectivated. Signs and symptoms were controlled on days 3 and 7 of treatment. In 42 patients, lesions specimens were taken for virus isolation. In 23 of them, cytopathic effect was detected (54.76%). Results showed a rapid relief from pain (p less than 0.05), ardor (p less than 0.01) and paresthesia (p less than 0.001) and also accelerated healing of vesicles in patients treated with interferon. Tendency to reduce the total time of the disease in those patients treated with IFN was observed.

Administration, Topical↗
PubMed1982

Catecholamines levels and parotid secretion in children with chronic atopic dermatitis.

The purpose of this study was to evaluate the in vivo state of both branches of the autonomic nervous system in children with chronic atopic dermatitis. In 15 patients, age 4 to 11, the following parameters were analyzed: (1) basal plasma levels of epinephrine, norepinephrine, and dopamine; (2) poststimulation (standing and i.v. furosemide administration); (3) basal urinary excretion of epinephrine, norepinephrine, and vainillin mandelic acid; (4) 30 min postfurosemide administration; (5) parotid secretory response to intraoral 0.1 m citric acid: flow rate, saliva pH, and concentrations of bicarbonate, chlorides, inorganic phosphates, total protein, and amylase activity. No differences in plasma and urinary basal levels of the catecholamines were observed. In response to standing, plasma norepinephrine from atopic children showed a greater increase than that seen in normal healthy children. From the salivary factors studied, no differences were found in parotid flow-rate, bicarbonates, chlorides, and inorganic phosphates. Protein concentration as well as amylase activity were significantly decreased in children with atopic dermatitis. These findings suggest that in atopic dermatitis, the beta-sympathetic mediated responses are impaired; on the other hand, parasympathetic mediated responses remain preserved.

Catecholamines↗
PubMed1980

The core subunit structure in RNA polymerase holoenzyme determined by neutron small-angle scattering.

The core subunit arrangement of alpha 2-beta-beta' within DNA-dependent RNA polymerase holoenzyme alpha 2 beta beta' sigma from Escherichia coli was investigated by neutron small-angle scattering using label triangulation. The quaternary structure of multisubunit biomolecules can be studied by this new method if total reconstitution works in a quantitative way and if extensive replacement of C-bound hydrogen (H) by deuterium (2H) is possible. A substitution of the selected subunits by their fully deuterated analogues was used for the analysis of the overall shapes of the core subunits, alpha 2, beta and beta' in situ and for the determination of the intersubunit centre-to-centre distances. The contrast between the buffer and the remaining 'hydrogenated' enzyme vanishes if the buffer contains 42% 2H2O (matching of scattering length densities). The isotopic hybridization of the enzyme fulfils the conditions of isomorphous replacement as required: molecular functions, like enzyme activity, were completely preserved. The orientations of the core subunits within the holoenzyme were derived by comparing theoretical and experimental pair distance distribution functions, P(r), obtained from the scattering intensity differences of the pair-labelled (e.g. both beta and beta' labelled) and both mono-labelled molecules by direct Fourier transformations. Additional, the subunit shapes were refined by P(r) analyses. The arrangement of the stable core structure within the holoenzyme, which contains sigma as a dissociable factor, is presented in a three-dimensional model.

DNA-Directed RNA Polymerases↗
PubMed1978

Experimental evidence for secondary protein-chromophore interactions at the Schiff base linkage in bacteriorhodopsin: Molecular mechanism for proton pumping.

Resonance Raman spectroscopy of the retinylidene chromophore in various isotopically labeled membrane environments together with spectra of isotopically labeled model compounds demonstrates that a secondary protein interaction is present at the protonated Schiff base linkage in bacteriorhodopsin. The data indicate that although the interaction is present in all protonated bacteriorhodopsin species it is absent in unprotonated intermediates. Furthermore, kinetic resonance Raman spectroscopy has been used to monitor the dynamics of Schiff base deprotonation as a function of pH. All our results are consistent with lysine as the interacting group. A structure for the interaction is proposed in which the interacting protein group in an unprotonated configuration is complexed through the Schiff base proton to the Schiff base nitrogen. These data suggest a molecular mechanism for proton pumping and ion gate molecular regulation. In this mechanism, light causes electron redistribution in the retinylidene chromophore, which results in the deprotonation of an amino acid side chain with pK >10.2 +/- 0.3 (e.g., arginine). This induces subsequent retinal and protein conformational transitions which eventually lower the pK of the Schiff base complex from >12 before light absorption to 10.2 +/- 0.3 in microseconds after photon absorption. Finally, in this low pK state the complex can reprotonate the proton-deficient high pK group generated by light, and the complex is then reprotonated from the opposite side of the membrane.

Journal Article↗
PubMed1976

Resonance raman studies of a c type algal cytochrome. Deuterium shifts and a comparison with mammalian cytochrome c.

A c type cytochrome isolated from Synechococcus lividus grown on water and 2H2O media, has been studied by resonance Raman spectroscopy. The spectra were taken on the oxidized and reduced protein with excitation within the Soret band at 441.6 nm to determine whether individual resonance Raman bands of the heme shift upon deuterium substitution and also to provide a comparison with the spectra of horse heart cytochrome c. Some of the shifts observed with the deuterated heme c are larger than the corresponding shifts in meso-deuterated metalloporphyrins suggesting mixing of peripheral substituent vibrations with the skeletal modes of the porphyrin macrocycle. The algal cytochrome exhibits resonance Raman spectra roughly similar to those of horse heart cytochrome c, consistent with its optical absorption spectra which is typical of c type cytochromes, although a detailed comparison reveals note-worthy differences between the spectra of the two proteins; this may be a reflection of the effect of non-methionine ligands and protein environment on the vibrations of the c type heme in the algal cytochrome.

Animals↗
PubMed1975

Ionic base radicals in gamma-irradiated oriented non-deuterated and fully deuterated DNA.

The free radicals induced by gamma-irradiation at 77 K in non-deuterated and fully deuterated oriented samples of moist algal DNA have been studied by electron paramagnetic resonance (e.p.r.). The e.p.r. spectra from the non-deuterated sample were found to be similar to those from calf-thymus DNA studied previously. Numerical spectra simulations were performed based on the previously proposed interpretation of the DNA spectra at 77 K in terms of a mixture of two spectral components arising from anionic and cationic base radicals (probably on thymine and guanine, respectively). The simulations were found to account satisfactorily for the main characteristics of the e.p.r. spectra from both the non-deuterated and the fully deuterated algal DNA sample.

Cobalt Radioisotopes↗