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Biomedical subjects

O Buchardt

Publications and source records attributed to O Buchardt.

At least 55 records · Page 3Linked to original sources
PubMed1986

Synthesis, tissue distribution and cytostatic properties of two new daunorubicin derivatives of 2-thiouracil containing a guanidine bridge.

In further attempts to utilize the affinity of 2-thiouracil for melanin-producing tissues in the design of drugs active against malignant melanomas, guanidine-bridged adducts of the anthraquinone drug daunorubicin (1a) with 2-thiouracil were prepared (Scheme 3). The expected adduct (4), and a by-product in its preparation (5) (Scheme 3), were inactive against murine melanoma, in vivo, and did not show affinity for melanin-producing tissues. They were efficient DNA intercalating agents, but were much less cytostatic than daunorubicin against Cloudman melanoma, and were inactive, in vitro, against human cervical carcinoma MS 751. The coupling chemistry employed may have application in current attempts to effect binding of drugs to high molecular weight targeting antigens.

Animals↗
PubMed1985

Photochemical crosslinking of protein and DNA in chromatin. II. Synthesis and application of psoralen-cystamine-arylazido photocrosslinking reagents.

The synthesis and testing of a new type of nucleic acid-protein photocrosslinking reagent is described. The reagents are composed of a psoralen ligand for nucleic acid photoattachment, which is linked to an azidobenzoyl group, for protein photoattachment. The linker contains a disulfide bridge which can be opened by reduction with mercaptans. The reagents were tested in a chromatin system, where it was found that they induced cleavable crosslinks between the histones and the DNA upon irradiation with long-wavelength ultraviolet light (lambda greater than 300 nm).

Azides↗
PubMed1985

Psoralenamines. 3. Synthesis, pharmacological behavior, and DNA binding of 5-(aminomethyl)-8-methoxy-, 5-[[(3-aminopropyl)oxy]methyl]-, and 8-[(3-aminopropyl)oxy]psoralen derivatives.

A series of derivatives of 5-(aminomethyl)-8-methoxypsoralens, 8-[(3-aminopropyl)oxy]psoralens, and 5-[[[3-(tri-methylammonio)propyl]methyl]-8-methoxypsoralen has been synthesized and their potential as PUVA reagents examined. While the DNA association constants of selected psoralens were found to be 10(5)-10(6)L mol-1, corresponding to efficient binding, flow linear dichroism studies indicated that only the 8-substituted psoralens bind to DNA by intercalation. Furthermore, the ability to photoinduce interstrand cross-links in calf thymus DNA, in vitro, was as efficient as that of 8-methoxypsoralen for the 8-substituted psoralens, which were up to 25 times as efficient as the 5-substituted psoralens. Four of the psoralens studied were radiolabeled and used to study photobinding to DNA. Analogously to the cross-binding results, the 8-substituted psoralens were more efficiently photobound than the 5-substituted, while only slight differences were found in the photobinding-cross-linking ratio. The photoreactivity of the aminopsoralens toward cyclohexene and 2'-deoxythymidine was enhanced compared to that of 8-methoxypsoralen, the effect being most pronounced when the amino group is close to the furocoumarin ring system. Most of the new compounds were less photocytotoxic than 8-methoxypsoralen to NHIK 3025 cells, in vitro, and they caused less light-induced DNA interstrand cross-linking, in situ, in these cells. A clear correlation between the photocytotoxicity and the DNA cross-linking ability of the psoralens was observed. Several of the derivatives showed more pronounced effects in the light-dependent skin thickening (inflammatory) test on mice than 8-methoxypsoralen. No correlation between DNA cross-linking capacity, in vitro, and skin phototoxicity was found for this series of psoralens.

Animals↗
PubMed1984

Photochemical cross-linking of protein and DNA in chromatin. Synthesis and application of a photosensitive cleavable derivative of 9-aminoacridine with two photoprobes connected through a disulphide-containing linker.

A novel cleavable photo-cross-linking reagent, N-(2-methoxy-6-azidoacridin-9-yl)-N'-(4-azidobenzoyl)cystamine, for analysis of protein-nucleic acid interactions, has been synthesized. The reagent contains two photosensitive groups that can be activated sequentially. The azidoacridinyl moiety is sensitive to u.v. and visible light (lambda less than or equal to 450 nm), whereas the azidobenzoyl part needs higher-energy light (lambda less than or equal to 350 nm). Furthermore, the disulphide bridge connecting the two photoactive groups can be cleaved by reduction with mercaptans. The reagent is shown to induce cleavable cross-links between all five major histones and DNA in chromatin from Ehrlich ascites cells on activation with long-wavelength u.v. light (lambda greater than 300 nm) at an efficiency of approximately 3% of the added reagent.

Azides↗
PubMed1983

Acridine-psoralen amines and their interaction with deoxyribonucleic acid.

A series of novel compounds in which a 9-acridinyl nucleus is linked to a psoralen nucleus in the 5- or 8-position via polyamines was prepared and examined. Their reversible binding to DNA and their irreversible binding to DNA and DNA cross-linking upon irradiation with UV-A light were examined. It was found that they were all less efficiently photoreactive than 8-methoxypsoralen (8-MOP), both in cross-linking and photobinding to DNA, whereas the ratio between their photobinding and cross-linking was 40-400 times that of 8-MOP. Compounds in which the linker was attached to the 5-position in psoralen showed smaller cross-linking and photobinding efficiencies and larger ratios between photobinding and cross-linking than those of psoralens attached in the 8-position. This strongly indicates that the 9-substituents of the acridines are oriented toward the minor groove. Flow linear dichroism studies showed that the compounds were DNA intercalating with the acridine moiety, whereas the psoralen moiety in no case was clearly intercalating. This conclusion was further supported by viscometry which also strongly indicated monointercalation.

Acridines↗
PubMed1983

9-acridinyl and 2-methoxy-6-chloro-9-acridinyl derivatives of aliphatic di-, tri-, and tetraamines. Chemistry, cytostatic activity, and schistosomicidal activity.

9-acridinyl derivatives of 1,6-hexanediamine, 1,8-octanediamine, bis(3-aminopropyl)amine, N,N'-bis(3-amino-propyl)piperazine, and N-ethyl-1,6-hexanediamine in the form of their hydrochlorides were prepared in high yields and converted into potential hetero bis DNA intercalating diacridines. The corresponding potential homo bis DNA intercalating reagents were prepared by heating the above amines with 9-chloroacridines. The chemical stability of the acridines was examined. Their cytostatic activity against Cloudman melanoma cells, in vitro, has been determined. The strongest cytostatic activity was observed for the acridine derivatives of the tri- and tetraamines. The schistosomicidal activity of selected acridine and diacridine derivatives against Schistosoma mansoni in mice was found to be insignificant. The S. mansoni egg development was apparently suppressed by this treatment.

Aminoacridines↗
PubMed1982

Affinity therapeutics. 1. Selective incorporation of 2-thiouracil derivatives in murine melanomas. Cytostatic activity of 2-thiouracil arotinoids, 2-thiouracil retinoids, arotinoids, and retinoids.

The incorporation of 2-[35S]thiouracil and two of its derivatives into murine melanomas, in vivo, was studied. It was confirmed [J. R. Whittaker, J. Biol. Chem., 246, 6217--6226 (1971)] that 2-thiouracil has a marked affinity for melanin-producing tissue and that an affinity for such tissue could be sustained by 5-substituted 2-thiouracils. A series of derivatives of arotinoids and retinoids, with or without a 2-thiouracil group as a potential carrier to obtain affinity for melanomas, was examined for cytostatic activity, in vitro. None of these showed significant activity against murine melanomas.

Animals↗
PubMed1981

Tolfenamic acid. Detection and structure of urinary metabolites.

N-(2-Methyl-3-chlorophenyl)anthranilic acid (tolfenamic acid) and its metabolites in serum and urine were analyzed by a reversed-phase ion-pair HPLC method. The major metabolites were N-(2-methyl-3-chloro-4-hydroxyphenyl)anthranilic acid, and one of the minor metabolites was N-(2-formyl-3-chlorophenyl)anthranilic acid, i.e., products resulting from hydroxylation in either the methyl group or the methylchlorophenyl group of tolfenamic acid, and further oxidation of the hydroxymethyl group to a formyl group.

Adult↗
PubMed1979

Analogues of [3H] chloramphenicol for photoaffinity labeling.

The synthesis of [3H]chloramphenicol and its erythro-diastereoisomer with specific activities of 1.25 Ci/mmol, and the further transformation of the [3H]chloramphenicol to a series of azido and diazo-substituted derivatives are described. The antibiotic activity of the compounds was considered insufficient for their use as photoaffinity labels.

Affinity Labels↗
PubMed1975

Light sensitive chloramphenicol analogues.

Some chloramphenicol analogues have been prepared in order to find reagents which could be used in a photoaffinity labelling study of the peptidayl transferase center of the E. coli ribosome. The compounds were tested for antibiotic activity in vitro in the "fragment reaction" assay, and for their ability to generate very reactive species upon irradiation.

Chloramphenicol↗
PubMedDate not supplied

Solid-phase synthesis of peptide nucleic acids.

Peptide nucleic acids (PNA) were synthesized by a modified Merrifield method using several improvements. Activation by O-[benzotriazol-1-yl]-1,1,3,3-tetramethyluronium hexafluorophosphate in combination with in situ neutralization of the resin allowed efficient coupling of all four Boc-protected PNA monomers within 30 min. HPLC analysis of the crude product obtained from a fully automated synthesis of the model PNA oligomer H-CGGACTAAGTCCATTGC-Gly-NH2, indicated an average yield per synthetic cycle of 97.1%. N1-benzyloxycarbonyl-N6(3)-methylimidazole triflate substantially outperformed acetic anhydride as a capping reagent. The resin-bound PNAs were successfully cleaved by the 'low-high' trifluoromethanesulphonic acid procedure.

Base Sequence↗
PubMedDate not supplied

The oxidative cleavability of protein cross-linking reagents containing organoselenium bridges.

The intensive use of cleavable cross-linking reagents to study macromolecular biological interactions has shown a demand for optimizing these reagents in such a way that the involved macromolecules remain intact. The present work focuses on the development of selenium linkers that are cleavable by mild oxidation. The efficiency of cross-linking and subsequent cross-linker cleavage with a new series of such homo- or heterobifunctional cross-linking reagents have been tested in a simple model system, consisting of albumin and cytochrome c. Resultant, or residual, covalent complex formation is examined by SDS-polyacrylamide gel electrophoresis. From this work it can be concluded that diallyl selenides are readily cleaved by mild oxidation, whereas dialkyl selenides and benzyl alkyl selenides can only be cleaved when the alkyl part of the selenide has an electron-withdrawing group next to the beta-carbon from selenium.

Animals↗
PubMedDate not supplied

Photolytic cleavage of DNA by nitrobenzamido ligands linked to 9-aminoacridines gives DNA polymerase substrates in a wavelength-dependent reaction.

A series of reagents containing 3- or 4-nitrobenzamido ligands tethered to 9-aminoacridine via variable-length linkers have been prepared and their properties as photochemical DNA cleavers (photonucleases) examined. When irradiated with approximately 300-nm light, where the nitrobenzamido ligand can absorb, they cleave DNA in an oxygen-independent reaction presumably involving oxygen transfer from the nitro group to the deoxyribose units of the DNA backbone (Nielsen et al., 1988b). This reaction is pH independent and only slightly affected by the linker length, and the DNA fragments are not substrates for DNA polymerase. When approximately 420-nm light is used, were only the 9-aminoacridinyl ligands absorb, the DNA cleavage is also oxygen-independent but pH dependent, requires DNA saturation with the reagent (base pair:reagent less than or equal to 2), and is most efficient with the longer linkers. The cleavage is specific for guanine residues and results in 5'-phosphate termini and heterogeneous (more than four products) 3'-termini. One of the products is presumably 3'-hydroxy since DNA photocleaved with nitrobenzamido acridine reagents and 420-nm radiation are substrates for DNA polymerase in a nick translation assay as well as for the Klenow fragment. An electron-transfer mechanism is suggested.

Aminoacridines↗