Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Testosterone (17β-hydroxy-4-androsten-3-one) was studied by the semiempirical AM1 and PM3 and ab initio STO-3G*, 3-21G*, and 6-31G* methods. The goals were to compare those methods and to know the electronic structure of the hormone. Full geometry optimization was performed, and two crystal conformers (T1 and T2), and experimental dipole moment in solution were used for comparison. One conformer with a dipole moment similar to the solvated conditions was generated. Total energy, entalphies, dipole moments, charges, electrostatic potentials, and highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbital (LUMO) were calculated. Root-mean-square (RMS) index of the theoretical molecules against T1 and T2 showed best results with the 3-21G* and 6-31G* methods, while AM1 gave better energies than PM3. Dipole moments were directed toward the OH group and the botton face of the A ring. The frontier orbitals were located along the C4-C5 π bond, particularly the LUMO was split between C4 and C5, predicting the action of enzymes at C5 yielding to 5α and 5β-reduced androgens. Electrostatic potentials might be also of biological importance since they are coincidental with the dipole-moment orientation. Finally, it is interesting that the solvatedlike conformer, its properties, and the OH group laid between the same group of T1 and T2 and with a total energy between the crystals and the gas phase or in vacuo conditions. This results might also explain the biology of testosterone and use them to model the hormone-receptor interaction. © 1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0020-7608
    Keywords: progesterone ; 5α-progestins ; allopregnanedione ; allopregnanolone ; tetrahydroprogesterone ; electronic structure ; ab initio calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Progesterone (P) yields to 5α-reduced progestins, namely 5α-pregnanedione (DHP), tetrahydroprogesterone (THP), and allopregnanolone (ALLO-P). The geometries and electronic structure of these steroids were assessed by ab initio calculations using the 6-31G* basis set. The parameters measured were bond distances, valence angles, and dihedral angles. Likewise, the following were calculated: total energy; frontier orbitals, i.e., highest occupied molecular orbital (HOMO); lowest unoccupied molecular orbital (LUMO); dipole moment; atomic charges; and electrostatic potentials. The frontier orbitals of P were located at the π-double bond. However, the HOMO of the 5α-progestins was extended into the molecule, while the LUMO was confined at the C20 carbonyl group. The atomic charges, electronic density surfaces and electrostatic potentials showed patterns according to the stereochemical arrangement of the C3 and C20 carbonyl and hydroxyl functional groups. Interestingly, P and THP showed the larger dipole moment and high electronic density at the A-ring because the double bond and the 3α-hydroxy group, respectively. The present results might explain to some extent the metabolism of the studied progestins. Similarly, some physicochemical properties, such as dipole moments and electrostatic potentials, seem related with important biological actions such as uterine contractility and control of gonadotropin secretion.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 329-338, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Etiocholanes are metabolites of androstenedione (4-androsten-3,17-dione) and testosterone (17β-hydroxy-4-androsten-3-one). These compounds are produced by the action of 5-reductases which break the π double bond of the androstenes at C4 and C5. The most important etiocholanes are 5β-androstanedione (etiocholanedione), 3α-hydroxy-5β-androstan-17-one (etiocholanolone), 3β-hydroxy-5β-androstan-17-one (epietiocholanolone), and 17β-hydroxy-5β-androstan-3-one (5β-dihydrotestosterone; 5βDHT). Among their most important biological effects are depression of the central nervous system, relaxation of smooth muscle, and stimulation of sexual behavior. The intent of the present study is a determination of the effects of carbonyl and hydroxyl groups at C3 and C17 on the electronic structure of these androgens, in an attempt to gain some insight into their biological action. All calculations were of the semiempirical AM1 type. The decrease of enthalpy caused by an hydroxyl group was found to be twice that of a carbonyl group. The effect of two groups was found to be additive. Carbonyl groups on the other hand led to an increase of dipole moment and of the electrostatic charges on neighboring carbons that were higher than those produced by hydroxyl groups. Carbonyl groups at C17 pushed the highest occupied molecular orbital (HOMO) to higher energy whereas a carbonyl at C3 had little or no effect. However, in mono and di-keto structures, both HOMO and lowest unoccupied molecular orbital (LUMO) were located as expected closer to the carbonyl group. Etiocholanedione, a diketo structure, showed degeneracy of frontier orbitals with its related HOMO-1 and LUMO+1. Structures with mono-hydroxyl or di-hydroxyl functional groups showed the lowest HOMO values; the highest LUMO values and quasi degeneracy of HOMO-1 and LUMO+1. The HOMO and LUMO of etiocholane and for the mono and di-hydroxyl structures were observed diffused throughout the molecules in a “sausagelike” or “ribbonlike” fashion. These results might explain some metabolic steps. Likewise, the difference of intermolecular forces, i.e., dipole moments and charges displayed by the carbonyl and hydroxyl groups, might help to elucidate some biological effects.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 64: 249-254, 1997
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...