Biomedical subjects

C Nave

Publications and source records attributed to C Nave.

40 records · Page 3Linked to original sources

PubMed1981

Structure of the protein and DNA in fd filamentous bacterial virus.

The virion of filamentous bacterial viruses comprises a cylindrical protein shell of o.d. approximately 60 A and i.d. 20A, containing a single-stranded circular DNA molecule which has two oppositely directed but not base-paired strands extending the length of the virion. The assembly of the virion involves an intracellular prepackaging of the DNA with a viral DNA-binding protein which is then displaced by the coat protein as the growing virion crosses the bacterial membrane. Studies of the virion by X-ray fibre diffraction show that the protein coat consists largely of alpha-helices oriented roughly parallel to the axis of the virion. As the normal to a planar peptide tends to align normal to a magnetic field, it is possible to improve significantly the orientation of virions in fibres using a strong magnet. The success of this technique with the Pf1 strain of virus led us to apply it to the better-known fd (f1, M13) strain. We report here new information about the arrangement of protein and DNA in the fd virion obtained from the improved diffraction pattern (Fig. 1).

Bacteriophages↗

PubMed1979

Macromolecular structural transitions in Pf1 filamentous bacterial virus.

The filamentous bacterial virus Pf1 is a simple model for biological filaments. We have studied the structure of the virion and report here that the helix parameters of Pf1 change sharply with temperature at about 8 degrees C. Local interactions between protein subunits change by only a few tenths of an angstrom, but the changes are amplified between one end and the other of the virion to a rotation of 15 turns and a translation of 1,000 A. The limited nature of the phase transition is probably due to the constraints of 'knobs-into-holes' interaction between side chains of adjacent alpha-helical protein subunits. Treatment of the virion with ether causes a rearrangement of protein subunits into sheets, with the alpha-helices normal to the plane of the sheet. This phase transition suggests a model for virion assembly in the bacterial membrane.

Bacteriophages↗

PubMedDate not supplied

The axial electron density in collagen fibrils from human corneal stroma.

Low angle synchrotron X-ray diffraction patterns were obtained from the demembranated human corneal stroma. These patterns showed differences in the relative intensities of the meridional reflections compared to those obtained using bovine corneas. In particular, the first order reflection, conspicuously absent in the bovine pattern, is present in the human, although it is still only one third as intense as the first order in the pattern from rat tail tendon. Using phases deduced from the electron-optical images of negatively stained corneal collagens, a difference electron density map between bovine and human corneal collagen was drawn. The features in this map are explained in terms of a different inter-relationship between collagen and proteoglycans in the two species. The function of these species differences is unknown.

Animals↗

PubMedDate not supplied

[Ergometric test in the diagnostic and prognostic evaluation of arrhythmia].

One thousand three hundred patient's stress tests were analyzed to value arrhythmia outline and its relationship with anamnesis and clinical data. The patients were divided into two groups: group A, with no arrhythmias at rest, and group B with arrhythmias at rest. All classic nosographic arrhythmias were considered. In some teenager patients with arrhythmias at rest and no organic cardiopathy, anomalies disappeared during stress, showing the benignity of the phenomenon. Supraventricular stress induced arrhythmias has 1.2% of incidence in normal subjects, but 81% in heart disease patients. Supraventricular tachycardia was induced in 6 patients. Ventricular stress induced arrhythmias are found in 4.9%. Two cases of sudden death occurred in our groups.

Adolescent↗