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Biomedical subjects

N Camerman

Publications and source records attributed to N Camerman.

At least 55 records · Page 3Linked to original sources
PubMed1978

Molecular structure of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea.

The three-dimensional structure of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea (MeCCNU, NSC-95441), an effective antitumor agent, has been determined by single-crystal x-ray diffraction. MeCCNU crystallizes in monoclinic space group P21/c, with cell dimensions a = 12.387, b = 10.810, and c = 10 .198 A , beta = 102.62 degrees , and Z = four molecules per unit cell. The structure was solved by direct phasing procedures and refinement by anisotropic least squares converged at a discrepancy index R = 0.065. The cyclohexyl ring is in the chair conformation with the plane of the nitrosourea moiety twisted approximately 90 degrees from the cyclohexyl ring. The carbon-nitrogen bonds of the urea group are significantly asymmetric.

Chemical Phenomena↗
PubMed1977

Ethylphenacemide and phenacemide: conformational similarities to diphenylhydantoin and stereochemical basis of anticonvulsant activity.

The three-dimensional molecular structures of the potent anticonvulsant agents phenacemide and ethylphenacemide have been determined by single-crystal x-ray diffraction. Although these compounds possess straight-chain acetylurea groupings, in the crystalline state both molecules adopt a pseudocyclic conformation of the acetylurea chain through amide...carbonyl oxygen intramolecular hydrogen bonding. This results in spatial positioning and relative orientation of two electron-donating functional groups in these molecules similar to those of comparable atoms in diphenylhydantoin and other heterocycle-containing anticonvulsants.

Anticonvulsants↗
PubMed1976

X-ray crystallographic studies of cyclophosphamide (NSC-26271) derivatives.

Molecular structures of 4-hydroperoxycyclophosphamide (4-hydroperoxy-CP) and of two stereoisomers of 4-hydroperoxyisophosphamide (4-hydroperoxy-IP) have been determined by X-ray crystallography. All compounds, synthesized by Dr. A. Takamizawa by ozonolysis of appropriate open-chain precursors, demonstrate in vivo and in vitro cytotoxicity. The structure results show that for 4-hydroperoxy-CP and both isomers of 4-hydroperoxy-IP the 4-hydroperoxy group is situated axial to the ring. In 4-hydroperoxy-CP and the isomer of 4-hydroperoxy-IP which is the major product of the ozonolysis, the phosphoryl oxygen is equatorial to the ring and trans to the C4-oxygen. A scheme is presented to account for the interconversion of the two 4-hydroperoxy-IP configurations. Since a stereoisomer with a hydroperoxy or hydroxy group equatorial has not been isolated from the ozonolysis synthesis or from the Fenton oxidation of cyclophosphamide (CP), the configuration with C4-oxygen axial which is found in 4-hydroperoxy-CP and both isomers of 4-hydroperoxy-I is probably more stable and may be the configuration of 4-hydroxy compounds formed by the in vivo oxidation of CP, isophosphamide, and trophosphamide (TP). The molecular structure of TP has also been elucidated. Comparison of the conformations of the three chloroethyl alkylating groups of this molecule with those of the two chloroethyl groups of other CP derivatives indicates that these groups are highly flexible and do not assume one favored conformation.

Chemical Phenomena↗
PubMed1973

Structure of a dinucleotide: thymidylyl-(5'-3')-thymidylate-5' (pTpT).

The crystal and molecular structure of the naturally occurring deoxyribose dinucleotide sodium thymidylyl-(5'-->3')-thymidylate-5' has been determined by x-ray diffraction. There are four molecules of dinucleotide and 52 water molecules in an orthorhombic unit cell of dimensions (in angstroms) a = 16.06, b = 15.13, c = 15.65, space group P2(1)2(1)2. There is a very high degree of conformational consistency between the two halves of the molecule when the dinucleotide is viewed as the combination of two 5'-mononucleotides. The planes of the two thymines are not parallel, but are tilted 38 degrees with respect to each other. An extensive system of hydrogen bonding exists involving the bases, waters, phosphates, and sodiums; no base-base hydrogen bonding occurs. The dinucleotide structural parameters should be of assistance in interpreting DNA fiber diagrams in terms of possible structures.

Fourier Analysis↗
PubMed1972

Triiodothyronine: the 3'iodine is proximal to the -ring in crystal structure conformation.

The crystal and molecular structure of the thyroid hormone L-triiodothyronine has been determined by x-ray diffraction. The two phenyl rings are almost perpendicular to each other, the acute angle between their normals being 82 degrees. The 3'-iodine is situated proximal to the alpha-ring, rather than distal as inferred from chemical studies. Theoretical calculations indicate this proximal conformation to be energetically favored over the distal one.

Iodine↗
PubMed1972

Three-dimensional structure of L-thyroxin.

The biological importance of L-thyroxin, the principal hormone secreted by the thyroid gland, is well established, but the mechanisms of thyroid-hormone action are still largely unexplained. We have crystallized L-thyroxin and determined its three-dimensional structure by x-ray crystallography in the hope that comparison of structures of active and inactive thyroid-hormone analogues will shed some light on hormone mechanisms. We compare the conformation of L-thyroxin to that of triiodo-L-thyronine, a thyroid hormone with greater activity.

Crystallography↗