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Bernd Giese

Publications and source records attributed to Bernd Giese.

12 recordsLinked to original sources
PubMed2003

Long term association of the cytokine receptor gp130 and the Janus kinase Jak1 revealed by FRAP analysis.

Signal transduction through cytokine receptors is mediated mainly by non-covalently associated Jak tyrosine kinases. By confocal microscopy, the cytokine receptor gp130 and Jak1, fused with either yellow (YFP) or cyan (CFP) fluorescent protein, were found to be colocalized predominantly at intracellular vesicular structures and at the plasma membrane. Quantitative fluorescence recovery after photobleaching (FRAP) analysis at the plasma membrane revealed equal mobilities for gp130-YFP and Jak1-YFP. Thus, Jak1-YFP diffuses like a transmembrane protein indicating that membrane-bound Jak1 does not exchange rapidly with cytosolic Jaks. Applying a novel dual-color FRAP approach we found that immobilization of gp130-CFP by a pair of monoclonal antibodies led to a corresponding immobilization of co-transfected Jak1-YFP. We conclude from these findings that Jak1, once bound to a gp130 molecule, does not exchange between different receptors at the plasma membrane neither via the cytoplasmic compartment nor via a membrane-associated state.

Animals↗
PubMed2003

Chemical restriction: strand cleavage by ammonia treatment at 8-oxoguanine yields biologically active DNA.

Cleavage of DNA single and double strands at an 8-oxoguanine-containing nucleotide occurs in 90 % yield if the modified oligonucleotide is treated with NH(3) and O(2) at 60 degrees C. The mechanism of this oxidative cleavage reaction was studied, and the reaction was applied to the generation of single-stranded overhangs on PCR-amplified DNA that can be ligated. As an example, the lac Z' gene was amplified by PCR with 8-oxoguanine modified primers, restricted by ammonia treatment, ligated into a plasmid vector, transformed in Escherischia coli cells, and screened for blue colonies. This method guarantees efficiencies comparable to the standard cloning procedure with restriction enzymes, and it allows the design of any 3'-overhang independent of the sequence of the cloned DNA.

Ammonia↗
PubMed2003

Sequentially photocleavable protecting groups in solid-phase synthesis.

[reaction: see text] A sequential solid-phase peptide synthesis was developed using both photolabile linker and protecting groups. The chromatic sequential lability between a tert-butyl ketone-derived linker (sensitive to irradiation at 305 nm) and a nitroveratryloxycarbonyl (NVOC) group (sensitive at 360 nm) was exploited to prepare Leu-Enkephalin in a 55% overall yield. This new strategy allows the preparation of peptides in essentially neutral medium, by avoiding the use of common deprotection reagents such as trifluoroacetic acid or piperidine.

Journal Article↗
PubMed2003

Mutations in CLCN2 encoding a voltage-gated chloride channel are associated with idiopathic generalized epilepsies.

Idiopathic generalized epilepsy (IGE) is an inherited neurological disorder affecting about 0.4% of the world's population. Mutations in ten genes causing distinct forms of idiopathic epilepsy have been identified so far, but the genetic basis of many IGE subtypes is still unknown. Here we report a gene associated with the four most common IGE subtypes: childhood and juvenile absence epilepsy (CAE and JAE), juvenile myoclonic epilepsy (JME), and epilepsy with grand mal seizures on awakening (EGMA; ref. 8). We identified three different heterozygous mutations in the chloride-channel gene CLCN2 in three unrelated families with IGE. These mutations result in (i) a premature stop codon (M200fsX231), (ii) an atypical splicing (del74-117) and (iii) a single amino-acid substitution (G715E). All mutations produce functional alterations that provide distinct explanations for their pathogenic phenotypes. M200fsX231 and del74-117 cause a loss of function of ClC-2 channels and are expected to lower the transmembrane chloride gradient essential for GABAergic inhibition. G715E alters voltage-dependent gating, which may cause membrane depolarization and hyperexcitability.

Adolescent↗
PubMed2002

Recent developments of charge injection and charge transfer in DNA.

The question of whether and how electrons migrate through DNA was a matter of controversial discussion over the last ten years. Today, there is no doubt that long distance charge migration through DNA exists and most scientists explain this process by a multistep hopping mechanism. This feature article presents recent developments of our group on the injection of a positive charge into DNA bases and the transfer of the charge between the DNA bases. The influence of the donor, the nature of the bridge, and the distance between the donor and the acceptor are discussed.

DNA↗
PubMed2002

Density functional theory and surface enhanced Raman spectroscopy characterization of novel platinum drugs.

There is considerable interest in the development of novel platinum-based anticancer drugs that overcome the disadvantages associated with the widely used drug cisplatin, which are its inactivity against some types of tumors and its toxic side effects. In this study we show the suitability of normal Raman spectroscopy (NRS) and surface enhanced Raman spectroscopy (SERS), assisted by density functional theoretical (DFT) calculations, for the characterization of Pt complexes. The Pt complexes studied include the established drugs cisplatin and carboplatin, as well as five novel Pt complexes with anticancer activity. DFT calculations at the B3LYP/LanL2DZ level are a good prediction of the experimental NRS spectra of small and medium sized Pt complexes. The use of SERS allows the investigation of Pt complexes at physiological concentrations, and the binding strengths of the different ligands can be determined. The formation of positively charged hydrolysis products may be necessary for SERS activity. The exiting group in the hydrolysis reaction can be identified.

Antineoplastic Agents↗
PubMed2002

Rapid photolytic release of cytidine 5'-diphosphate from a coumarin derivative: a new tool for the investigation of ribonucleotide reductases.

In order to study the long-range radical transfer in the Escherichia coli ribonucleotide reductase (RNR), caged cytidine 5'-diphosphate (CDP) 1 was synthesized, which contains the photolabile (7-diethylaminocoumarin-4-yl)methyl moiety. The caged CDP 1 triggers the release of CDP when irradiated at wavelengths between 365 and 436 nm. The rate constant of the formation of alcohol 2 and cytidine 5'-diphosphate 3 is 2x10(8) s(-1) and the quantum efficiency for the disappearance of caged CDP 1 is 2.9%.

Coumarins↗
PubMed2002

Electron transfer in DNA.

Electrons migrate over long distances along the DNA in a multistep hopping process where the rate of each step depends strongly upon its length. The efficiency of this process is not only determined by the electron transfer rates but also by competing reactions with water, in which the charge carriers are trapped. Because electron transfer through DNA can occur under the conditions of oxidative stress, biological consequences are highly likely. In addition, it has been observed that some DNA-binding enzymes influence this charge transport. The question of whether DNA is a suitable material for nanolelectronic devices remains unanswered.

Adenine↗
PubMed2001

Long-distance electron transfer through DNA.

DNA molecules are able to transport electrons over long distances. In most experiments the process is stimulated by the oxidation of guanines (G), which generates guanine radical cations. The electron transport through DNA occurs in a multistep hopping mechanism with all Gs as carriers of the positive charge. The rate of each individual hopping step between the Gs decreases strongly with increase of the distance. If the (A:T) bridges between the guanines are long, adenines (A) also become charge carriers. Mismatches, single strands, and G-oxidation products can drastically diminish the efficiency of the charge transport. But in triplexes and DNA/RNA duplexes, as well as in several duplex DNA/peptide complexes, the efficacy of the charge transport is less affected. The ability of DNA molecules to transport charges over long distances could provide a mechanism for ameliorating the harmfulness of damage to DNA under the conditions of oxidative stress.

Adenine↗
PubMed1999

C-3'-Branched Thymidines as Precursors for the Selective Generation of C-3'-Nucleoside Radicals.

C-3'-nucleoside radicals can be generated via Norrish type I photocleavage of C-3'-acyl nucleoside derivatives. In monomer experiments employing C-3'-acylthymidine derivatives 2 and 3, a 1:1 mixture of isomers of the H-abstraction products was obtained when the photolysis was carried out in the presence of a hydrogen donor. Derivatives 2 were synthesized by an approach which involves the formation of a silyl-protected cyanohydrin, which is subsequently alkylated with organolithium reagents, followed by hydrolysis. Derivatives 3 could be obtained via a multistep synthesis starting from diol 7. Several different methods were attempted to oxidize the unprotected diol to the alpha-hydroxy aldehyde. Finally, a route was chosen which involves a protection-deprotection sequence followed by oxidation of the free primary alcohol. The resulting modified nucleosides should facilitate the study of C-3'-DNA radicals.

Journal Article↗
PubMed1998

Synthesis of Trehazolin from D-Glucose.

Trehazolin (2) is a specific inhibitor of trehalase, an enzyme that cleaves the reserve carbohydrates of many insects. We describe a short and efficient synthesis of trehazolin (2) and trehazolamine (5) that mimics its hypothetical biosynthesis. Starting molecule for the synthesis of trehazolamine (5) is glucose from which three chiral centers are conserved during the reaction sequence. The remaining two chiral centers of trehazolamine (5) are formed stereoselectively in a reductive cyclization of ketooxime ether 16 and the reduction of oxime ether 18. The overall yield of trehazolamine (5) is 22% over 8 steps from 15. The synthesis of trehazolin (2) from trehazolamine (5) follows a known procedure and is achieved in 63% over 3 steps.

Journal Article↗