Biomedical subjects

J W G Janssen

Publications and source records attributed to J W G Janssen.

3 recordsLinked to original sources

PubMed2004

Towards nuclear magnetic resonance micro-spectroscopy and micro-imaging.

The first successful experiments demonstrating Nuclear Magnetic Resonance (NMR) were a spin-off from the development of electromagnetic technology and its introduction into civilian life in the late forties. It was soon discovered that NMR spectra held chemically relevant information making it useful as an analytical tool. By introducing a new way of detection, moving away from continuous wave spectroscopy, Fourier Transform NMR helped to overcome sensitivity problems and subsequently opened the way for multi-dimensional spectroscopy. As a result NMR has developed into one of the most powerful analysis techniques with widespread applications. Still sensitivity is a limiting factor in the applicability of NMR. Therefore we witness a renaissance of technique development in magnetic resonance striving to improve its receptiveness. This tutorial review introduces the efforts currently made in miniaturizing inductive detection by designing optimal radio-frequency microcoils. A second approach is to introduce a new way of detecting magnetic resonance signals by means of very sensitive micromechanical force detectors. This shows that the detection limits in terms of absolute sensitivity or imaging resolution are still open to significant improvements.

Journal Article↗

PubMed2004

Implementing solenoid microcoils for wide-line solid-state NMR.

Solid-state nuclear magnetic resonance (NMR) probeheads using solenoid microcoils with an inner diameter of 300-400 microm are developed for the study of mass-limited solid samples. Some attention is paid to the mechanical ruggedness of the probes allowing sample changing. The performance, in terms of sensitivity and RF-characteristics, of these probeheads is studied for (1)H, (31)P, and (27)Al in different model compounds in view of the feasibility of specific applications. The results show that the sensitivity is high enough to detect approximately 10(14) spins/sqrt Hz with a signal-to-noise ratio of 1 in a single scan. A specific advantage of microcoils for solid-state NMR applications is that they can generate extremely high RF-fields if implemented in appropriate circuits. Using RF-powers in the hundreds of Watts range, RF-fields well in excess of 1MHz can be made. This allows the excitation of spectra of nuclei whose resonance lines are dispersed of several megahertz. This is particularly useful for quadrupolar nuclei experiencing large quadrupolar interactions as is demonstrated for (27)Al in single crystal and powdered minerals.

Computer-Aided Design↗

PubMed2002

Disruption of the RanBP17/Hox11L2 region by recombination with the TCRdelta locus in acute lymphoblastic leukemias with t(5;14)(q34;q11).

The t(5;14)(q33-34;q11) translocation constitutes a recurrent rearrangement in acute lymphoblastic leukemia involving the T cell receptor (TCR) delta locus on chromosome 14. Breakpoint sequences of the derivative chromosome 5 were isolated by application of a ligation-mediated PCR technique using TCR delta-specific primers to amplify genomic DNA from the leukemic cells of a patient with t(5;14). Through exon trap analysis, we identified various putative exons of the chromosome 5 target gene of the translocation; compilation of sequence information of trapped exons and available expressed sequence tags (ESTs) from the GenBank database allowed us to assemble 1.2 kb of the cDNA. Full-length cDNAs were isolated from a human testis cDNA library and sequence analysis predicted a putative Ran binding protein, a novel member of the importin-beta superfamily of nuclear transport receptors, called RanBP17. The t(5;14) breakpoint maps to the 3' coding region of the gene. The breakpoint of a second t(5;14) positive patient was mapped about 8 kb downstream of the most 3' RanBP17 exon and 2 kb upstream of the first exon of the orphan homeobox gene, Hox11L2. In both cases TCR delta enhancer sequences are juxtaposed downstream of the truncated or intact RanBP17 gene, respectively on the derivative chromosome.

Acute Disease↗