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D Hennig

Publications and source records attributed to D Hennig.

At least 19 recordsLinked to original sources
PubMed2000

Solitonic energy transfer in a coupled exciton-vibron system

We consider the exciton transfer along a one-dimensional molecular chain. The exciton motion is influenced by longitudinal vibrations evolving in a Toda lattice potential. It is shown how the soliton solutions of the vibron system coupled to the exciton system induce solitonic exciton transfer. To this aim the existence of a regime of suppressed energy exchange between the coupled excitonic and vibrational degrees of freedom is established in the case of which a nonlinear Schrodinger equation for the exciton variable is derived. The nonlinear Schrodinger equation possesses soliton solutions corresponding to coherent transfer of the localized exciton.

Journal Article↗
PubMed2000

Electron-vibron-breather interaction

We study the interaction of breathers in the context of a coupled electron-vibron lattice system. Starting with single-site excitations, it is demonstrated that constellations exist for which the coexistence of electronic and vibronic breathers is assured. The energy exchange between the vibrational and electronic subsystems and its impact on the breather formation are discussed in detail. The coupled electron-vibron dynamics shows a tendency toward energy redistribution into the vibronic degrees of freedom at the expense of the electronic energy content. Attention is paid to the relaxation dynamics in the energy exchange and we discuss the attainment of a steady regime for the coupled electron-vibron dynamics starting from a nonequilibrium state. It is demonstrated that the presence of breathers has a strong impact on the relaxation dynamics. Breathers can assist the relaxation process. With the help of a linear stability analysis, we show why the electronic subsystem acts as an energy donor while the vibron system serves as the energy acceptor. To this end we investigate the existence and stability of localized breathing eigenmodes capable of energy trapping. A frequency analysis reveals that strong exchange also occurs due to a temporal transition from single-frequency breathers to those oscillating with two frequencies and their temporal resonance interaction. Finally, the self-stabilized electron-vibron system relaxes to a combined electron-vibron breather. On increasing the electron-vibron coupling strength, only a vibronic phonobreather of large amplitude survives, whereas the electronic subsystem tends to energy equipartition.

Journal Article↗
PubMed1998

A formiminotransferase cyclodeaminase isoform is localized to the Golgi complex and can mediate interaction of trans-Golgi network-derived vesicles with microtubules.

A protein of 60 kDa (p60) has been identified using a quantitative in vitro vesicle-microtubule binding assay. Purified p60 induces co-sedimentation with microtubules of trans-Golgi network-derived vesicles isolated from polarized, perforated Madin-Darby canine kidney cells. Sequencing of the cDNA coding for this protein revealed that it is the chicken homologue of formiminotransferase cyclodeaminase (FTCD), a liver-specific enzyme involved in the histidine degradation pathway. Purified p60 from chicken liver has formiminotransferase activity, confirming that it is FTCD or an isoform of this enzyme. Isoforms of FTCD were identified in chicken hepatoma and HeLa cells, and immunolocalize to the region of the Golgi complex and vesicular structures in its vicinity. Furthermore, 58K, a previously identified microtubule-binding Golgi protein from rat liver (Bloom, G. S., and Brashear, T. A. (1989) J. Biol. Chem. 264, 16083-16092), is identical to FTCD. Both proteins co-purify with microtubules and co-localize with membranes of the Golgi complex. The capacity of FTCD to bind both to microtubules and Golgi-derived membranes may suggest that this protein, or one of its isoforms, might have in addition to its enzymatic activity, a second physiological function in mediating interaction of Golgi-derived membranes with microtubules.

Amino Acid Sequence↗
PubMed1991

Reassessment of the v-fms sequence: threonine phosphorylation of the COOH-terminal domain.

The v-fms oncogene product of the McDonough strain of feline sarcoma virus is a member of the receptor tyrosine kinase family. Its cellular counterpart, the c-fms product, is the receptor for colony-stimulating factor 1 (CSF-1) of macrophages. We have reanalyzed the v-fms gene by direct sequencing of a biologically active clone. An additional A nucleotide was detected in position 2810 of the published v-fms sequence. The frameshift changed the COOH-terminal sequence of the v-fms protein from -R-937-G-P-P-L-COOH to -Q-937-R-T-P-P-V-A-R-COOH. Antibodies against a synthetic peptide representing this new sequence precipitated the v-fms proteins from transformed NRK cells as well as from feline sarcoma virus (McDonough)-infected feline fibroblasts. We show by tryptic peptide mapping that threonine 939 present in the new sequence is phosphorylated by a yet unknown serine/threonine kinase in vivo. In chicken fibroblasts expressing the v-fms gene, this phosphorylation clearly depended on the addition of exogenous CSF-1. Furthermore, addition of CSF-1 appeared to activate the serine/threonine kinase, as judged by phosphorylation of the synthetic peptide QRTPPVAR.

Amino Acid Sequence↗
PubMed1988

Isolation of a transformation-defective mutant of the McDonough strain of feline sarcoma virus exhibiting tyrosine kinase activity in vitro but not in vivo.

NRK cells transformed by the McDonough strain of feline sarcoma virus (SM-FeSV) were mutagenized by the use of 5'-azacytidine. Four cell lines expressing different transformation-defective phenotypes were isolated. Superinfection of these cell lines with simian sarcoma-associated virus (SSAV) led in three instances to the recovery of transforming virus particles carrying an intact fms gene. A nonconditional transformation-defective virus, designated td26-SM-FeSV (SSAV), was isolated from one of the cell lines. NRK cells infected with this mutant contained actin cables and fibronectin networks and exhibited normal cell morphology. Such cells formed only small colonies in soft agar and exhibited a mitogenic activity similar to that of noninfected cells. Cells infected with td26-SM-FeSV (SSAV) synthesized a gag-fms fusion glycoprotein (gp180gag-fms). This polypeptide was processed in the normal manner into the intracellular gp120v-fms and a transformation-defective gp140td-v-fms which was expressed at the surface of infected cells. This species had an increased electrophoretic mobility on polyacrylamide gels compared with the molecule from wild-type virus.gp140td-v-fms had endo-beta-N-acetylglucosaminidase H-resistant carbohydrate side chains. No tyrosine kinase activity was detectable in vivo in td26-SM-FeSV (SSAV)-infected cells even when the cells were treated with sodium orthovanadate. In vitro, fms molecules from td26-SM-FeSV (SSAV)-infected cells exhibited tyrosine kinase activity as determined by autophosphorylation and phosphorylation of exogenous (poly)Glu-Tyr. At low ATP concentrations (less than 5 microM) this in vitro tyrosine kinase activity was significantly reduced compared with that of the wild-type counterpart.

Antigens, Surface↗
PubMed1987

[The effect of selected disintegrants on the properties of three hydrochlorothiazide tablet formulations].

The admixture of disintegrants was investigated in three different hydrochlorothiazide formulations with respect to tablet properties. Sodiumcarboxymethyl starchs, Na-CMS (Explotab, Primojel, Na-CMS AB-G.D.R.), cross-linked polyvinylpyrrolidone, CL PVP (Polyplasdone) and potato starch were applied. The investigations were especially aimed at the alteration of tablet properties in dependence on compressive force. Considering the values of decomposition and compressive strength Polyplasdone XL has been proved to be the most effective disintegrant for the hydrochlorothiazide formulations investigated. Potato starch shows the worst results. There are only slight differences between the three Na-CMS.

Drug Compounding↗