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Biomedical subjects

R Issac

Publications and source records attributed to R Issac.

5 recordsLinked to original sources

Radiation sources based on laser-plasma interactions.

Plasma waves excited by intense laser beams can be harnessed to produce femtosecond duration bunches of electrons with relativistic energies. The very large electrostatic forces of plasma density wakes trailing behind an intense laser pulse provide field potentials capable of accelerating charged particles to high energies over very short distances, as high as 1GeV in a few millimetres. The short length scale of plasma waves provides a means of developing very compact high-energy accelerators, which could form the basis of compact next-generation light sources with unique properties. Tuneable X-ray radiation and particle pulses with durations of the order of or less than 5fs should be possible and would be useful for probing matter on unprecedented time and spatial scales. If developed to fruition this revolutionary technology could reduce the size and cost of light sources by three orders of magnitude and, therefore, provide powerful new tools to a large scientific community. We will discuss how a laser-driven plasma wakefield accelerator can be used to produce radiation with unique characteristics over a very large spectral range.

Journal Article↗

The design of self-replicating helical peptides.

The self-assembly of helical peptides and information transfer through autocatalysis and cross-catalysis are the foundation of peptide-based molecular evolution models. Many fundamental properties of living systems, such as environmental sensitivity, chiroselectivity, cross-catalysis, dynamic error correction and conditional selection, are exhibited by various self-replicating peptide systems. Recently, advances have been made in the design of peptide systems with autocatalytic and cross-catalytic properties.

Amino Acid Sequence↗

Structure-function relationship in a beta-sheet peptide inhibitor of E47 dimerization and DNA binding.

A beta-sheet peptide inhibitor, 2H10, has been developed that inhibits the dimerization of the transcription factor E47. Inhibition of E47 dimerization has been demonstrated to also inhibit the DNA binding of this transcription factor. Truncated peptides based on 2H10 have demonstrated that the beta-sheet content of these peptides directly correlates with their inhibitory properties. Individual residues within 2H10 were identified that were responsible for the beta-sheet secondary structure by employing an alanine replacement strategy. The beta-sheet character of the alanine mutants also correlated well with their inhibition of E47 DNA binding. These results provide further evidence that interactions between the interfacial peptide inhibitors of E47 and the transcription factor itself are mediated by a beta-sheet structure.

Amino Acid Sequence↗

Phenotypic evidence for a common pathogenesis in X-linked deafness pedigrees and in Xq13-q21 deletion related deafness.

A structural cochlear abnormality has been observed by high resolution CT scanning in some families where X-linked deafness is segregating. We now present evidence that the same abnormality is present in a deaf patient who has a deletion within Xq21. This observation provides phenotypic evidence that the genotypic basis of deafness is the same in both patient groups. It is also likely that the perilymphatic fluid "gusher" abnormality may be common to both.

Child↗

Experience with bone marrow trephine biopsy.

One hundred and ten bone marrow trephine biopsies were studied from January 1987 to July 1989, using Zenker's acetic acid as fixative and routine paraffin embedding. Trephine biopsies were useful in differential diagnosis of cytopenias, especially when bone marrow aspiration was hypocellular or a dry tap, and in staging of lymphomas and multiple myeloma.

Biopsy, Needle↗