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L Wyns

Publications and source records attributed to L Wyns.

102 records · Page 6Linked to original sources
PubMed1981

The structural organization of dinucleosomes and oligonucleosomes. Electric dichroism and birefringence study.

The spatial organization of nucleosomes and linker DNA in dinucleosomes and oligonucleosomes of various chain lengths has been investigated through electric dichroism, birefringence and relaxation times measurements at low ionic strengths (0.5 to 2.2 mM). From the negative dichroism observed for all the samples, it is concluded that the nucleosome subunits in the oligonucleosome chain must lie with their disc planes closely parallel to the fibre axis. The large increase of the negative dichroism of dinucleosomes upon Hl removal is interpreted by the unwinding of the DNA tails and the internucleosomal segment. All the samples displayed, under bipolar pulses, a predominantly induced orientation mechanism.

Animals↗
PubMed1981

Protection of discrete DNA fragments by the complex H1-octamerhistones or H5-octamerhistones after micrococcal nuclease digestion.

Several authors, including ourselves, have reported the existence of chromatosomes with DNA size larger than 166 bp in bird erythrocyte chromatin. It was tempting to correlate this increased DNA size with the presence of histone H5. In order to substantiate this hypothesis, we performed a micrococcal nuclease digestion kinetic on: chicken erythrocyte chromatin, either native, selectively depleted from H1, or from H1 and H5; and rat liver chromatin, either native or partially H1 depleted. The comparative analysis of the lengths of DNA in the chromatosome size region led to the following conclusions: - denaturing gels clearly reveal a first discrete pause at 178 nucleotides in H1 depleted chicken erythrocyte chromatin as well as in partially H1-depleted rat liver chromatin, before the material accumulates at the next intermediate 166 nucleotide chromatosome pause. - the generation of all discrete chromatosome bands is critically dependent on low ionic strength conditions and low Ca++ concentrations during the digestion, suggesting it may result from the protection of DNA cleavage sites by histone H5 or H1, C or N terminal domains.

Animals↗
PubMed1981

Differences in rearrangements of H1 and H5 in chicken erythrocyte chromatin.

H1 can rearrange in chicken erythrocyte polynucleosomes in 80 mM NaCl buffers. These rearrangements have been studied by sedimentation analysis. H1 redistributes between polynucleosomes as well as between polynucleosomes and monosomes. In these rearrangements H1 molecules move to free DNA sites. In contrast to H1, the chicken erythrocyte specific lysine-rich histone H5 does not show any of these dynamic properties. This difference in mobility of H1 and H5 also manifests itself in the selective extraction of H1 from H1, H5 containing polynucleosomes by the cation-exchange resin AG 50W-X2 at 80 mM NaCl.

Animals↗
PubMed1980

Upon the observation of superbeads in chromatin.

There exist some indications that nucleases recognize "superbeads" in chromatin. We show that a chromatin extract of rat liver which contains so-called "superbead"-peaks can be separated in a Mg++ soluble and a Mg++ insoluble fraction. The Mg++ insoluble fraction contains the full complement of histones and the expected DNA fragments, but has lost the characteristic peaks in sucrosegradient profiles. These discrete peaks are found in the Mg2+ soluble fraction of the chromatin extract. We give evidence that these peaks are RNP particles on the basis of their protein- and nucleic acid contents.

Animals↗
PubMed1980

Histone H1 can be removed selectively from chicken erythrocyte chromatin at near physiological conditions.

Histone H1 was depleted selectively from chicken erythrocyte polynucleosomes, without any detectable concomitant loss of H5 or core particle histones. The depletion is performed with ion exchange resin at low ionic strength (80 mM NaCl). The nucleosomes did not slide during the procedure. In contrast to the native chromatin, H1 depleted polynucleosomes are completely soluble in the 5--600 mM NaCl range.

Animals↗
PubMed1978

Cross-linking of nucleosomal histones with monofunctional imidoesters.

Cross-linking experiments with the MONOfunctional imidoester methyl-acetimidate, in the pH range 7.0 - 8.0, on rat liver nucleosomes generate a cross-linking pattern almost identical with the one observed for much longer BIfunctional reagents (e.g. dimethylsuberimidate). Combined cross-linking and trypsin digestion experiments suggest that all or at least the great majority of this cross-linking occurs on trypsin digestible segments (or "tails") of the histones. The formation of oligomers over such extremely short distances and especially the observation of an H3 homodimer suggests a very close proximity of half-nucleosomes.

Animals↗
PubMedDate not supplied

Comparative filter binding study of H5 to nucleosome core particles, H1, H5 depleted chromatosomes and DNA fragments.

The filter-binding technique with PEI treated glass fiber is used to study the interaction of histone H5 to core particles, chromatosomes and DNA derived from it. By working at very low concentrations of interacting particles we are able to study the effective binding process independent of interfering insoluble complexes. The interactions are characterized by a very high affinity. An intrinsically higher affinity of H5 for cores and chromatosomes versus chromatosome derived DNA is demonstrated. Both chromatosomes and DNA derived from these bind about twice the amount as compared to core particles, which saturate at about one H5 per core particle.

Animals↗
PubMedDate not supplied

Comparison of llama VH sequences from conventional and heavy chain antibodies.

Forty different PCR clones encoding a llama variable heavy chain domain were analysed. The majority of these clones are derived from heavy-chain antibody cDNA in which the entire CH1 exon is absent. It appears from the amino acid within the VHH framework 1 and 3 that all the llama clones belong to the VH III family. However, the individual llama VHH sequences differ more substantially from each other than expected for members of the same family. Several remarkable amino acid substitutions in the framework 2 hinder the proper association of the VL. However, they lay the foundation for the secretion from the endoplasmic reticulum and good solubility behaviour of llama H2 antibodies. The repertoire of the llama VHHs may be extensive due to the presence of a long CDR3-loop, often constrained by a disulfide bridge and the occurrence of H1 and H2 loop conformations not yet encountered in mice or human VHs. The variability plot of the amino acids in the VHH shows that the first hypervariable region coincides with the structural H1 loop in contrast to the situation found in mice and man where the CDR1 and H1 are slightly offset. We propose that the amino acids of the llama H1 loop participate actively in the antigen binding. All these observations are characteristic for the llama VHHs of the homodimeric heavy-chain H2 antibodies, but are not maintained in the llama clones from conventional heterotetrameric H2L2 immunoglobulins.

Amino Acid Sequence↗