A phosphorus NMR study of the reaction products of cis-diamminedichloroplatinum (II) with a double-helical oligonucleotide and with DNA

AbstractThe structural distortion of oligonucleotides upon cis-PtCl2(NH3)2{d(T-C-T-C-G-G-T-C-T'-C-N7(5) N7(6)} reveals shifting of 4 phosphorus resonances due to platination. 3 Resonances could be assigned by selective 31P-irradiation, showing P(6) (P between the two Gs) to be shifted 1.5 ppm to low field. In the concomitant double strands P(6) is shifted 0.9 ppm to lower field. A similar peak has been observed in platinated salmon sperm DNA (37°C), indicating that Pt-binding to GpG-fragments in DNA is similar to that found for the decanucleotide, so the distortion of DNA might be comparable

Molecular mechanics studies of parallel and antiparallel phosphate-methylated DNA

Methylation of phosphate groups in oligo-dT strands leads to a parallel duplex with T · T base pairs. Molecular mechanics calculations on parallel d(TTTTTT)2 show it to be a symmetric right-handed helix with B-DNA conformational characteristics. Phosphate methylation stabilizes the duplex by ca. 41 kcal/mol, due to removal of the interstrand phosphate electrostatic repulsions. The chirality introduced with phosphate methylation is important for the molecular geometry, since RP methylation predominantly influences the conformation around the bond (PO3), while SP methylation mostly changes the conformation (PO5). This is also true in antiparallel helices with methylated phosphates, as is shown by molecular mechanics calculations on d(GCGCGC)2. These results may be of relevance to protein-DNA interactions, where phosphate charges are also shielded. As the pro-SP oxygen is most available in a right-handed helix, we suggest changes around the bond to occur upon protein complexation, leading to a widening of the major groove in the d(GCGCGC)2 duplex (from 12 to 13 Å) and reduced minor groove (from 6 to 5 Å)

Acquisition and Processing of Cerebral Blood Flow Data with a M;ultichannel Analyser and Microcomputer

The method of the determination of cerebral blood flow in dogs with radio-isotopes to evaluate ethrane as a new anaesthetic agent is described, as well as the use of a multichannel analyser and the programmes developed for the analysis of data in a conversational mode. Preliminary results of the use of the computer programme are presented

3α,4α-Ep­oxy-5α-androstan-17β-yl acetate

The title compound, C21H32O3, results from modifications of the A and D rings of the aromatase substrate androstenedione. Ring A adopts a conformation between 10β-sofa and 1α,10β half-chair. Rings B and C are in slightly flattened chair conformations. Ring D approaches a 13β-envelope conformation, probably due to the acet­oxy substituent, and shows a very short Csp 3—Csp 3 bond next to the epoxide ring, which is characteristic of 3–4 epoxides.

5α-Androst-3-en-17β-yl acetate

In the crystal structure of the title compound, C21H32O2, ring A is highly distorted, with a conformation inter­mediate between 10β-sofa and 1α,10β-half chair; rings B and C have slightly flattened chair conformations. Ring D assumes an unusual 13β-envelope conformation, probably induced by the acet­oxy substituent. Cohesion of the crystal structure is due only to weak van der Waals inter­actions

Super Epistolas canonicas cum postillis

Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 2006Procede de la desamortización del Monasterio de Santes Creus (Tarragona)Iniciales en rojo; las h. 47-76 v. forman un sólo tratad

Androstane-3β,5α,6β,17β-tetrol tri­hydrate

The title hydrated tetrol, C19H32O4·3H2O, was synthesized by stereoselective reduction of the compound 3β,5α,6β-trihy­droxy­androstan-17-one. All rings are fused trans. The organic mol­ecules are connected head-to-tail along the c axis via O—H⋯O hydrogen bonds. Layers of water mol­ecules in the ab plane inter­connect these chains. A quantum chemical ab initio Roothan Hartree–Fock calculation of the isolated mol­ecule gives values for the mol­ecular geometry close to experimentally determined ones, apart from the C—O bond lengths, whose calculated values are significantly smaller than the measured ones, probably a consequence of the involvement of the C—OH groups in the hydrogen-bonding network

5α,6α-Ep­oxy-7-norcholestan-3β-yl acetate

The title cholestan, C28H46O3, was prepared by epoxidation of 7-norcholest-5-en-3β-yl acetate and crystallized by slow evaporation from an ethano­lic solution. All rings are trans fused. The 3β-acetate and the 17β-cholestane side chain are in equatorial positions. The mol­ecule is highly twisted due to its B-nor characteristic. A quantum chemical ab-initio Roothaan Hartree–Fock calculation of the equilibrium geometry of the isolated mol­ecule gives values for bond lengths and valency angles in close agreement with the experimental ones