Structure of 6α-methyl-17α-hydroxyprogesterone butanoate,C26H38O4

The title compound crystallizes in space groupP2₁2₁2₁ with lattice constantsa=16.253(3),b=17.107(3), andc=8.486(2) Å. The A ring has 1,2-half-chair conformation. The calculated steric energy of a 6-methyl-17-ester progesterone molecule is lower by about 4 kJ/mol for the normal A-ring conformation. The progesterone side chain has typical conformation for 17-ester steroids; the C(16)-C(17)-C(20)-O(20) torsion angle is –24.9(4)°.     

Examination of Polish Identity Documents by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) was applied to the preliminary examination of Polish documents – passports and identity cards – for forensic purposes. Several security features of potentially high discrimination capability were selected at both the passports (Alphagram, serial number, the contour map of Europe, and emblem) and identity cards (kinegram, the date of birth, and emblem). Different elemental compositions were identified after comparing the spectra recorded from various measurement locations. It was possible to identify characteristic atomic emission from several elements (such as Ti, Ca, K, Fe, Cr, Mg, Na, La, Cd, Li, V, Al, Mn, Ni, and Cu) based on the type of document, issue date, and evaluated area. In the case of passports, the potentially good discriminators with unique elemental composition were identified, e.g., the serial number and the contour map of Europe printed with the use of intaglio printing technique. Identity cards with the cover of polycarbonate foil constitute a very difficult sample to analyze because of the foil’s influence on the laser ablation phenomenon. This study presents the potential of LIBS as an effective and useful technique to analyze Polish passports for forensic purposes. Its many advantages provide a good alternative to the analytical methods routinely used for the examination of these objects.     

Structure of 4-methoxy-4-cholesten-3-one,C28H46O2

The X-ray crystal structure of 4-methoxy-4-cholesten-3-one, C₂₈H₄₆O₂, has been determined. Final agreement factors wereR=0.057 andR _w =0.057 for 2912 reflections. The_A ring has a sofa-half-chair conformation, and the C4 side chain is turned under the steroid skeleton. The cholesterol side chain is fully extended, with agauche, trans conformation of the terminal C26 and C27 methyl groups.     

Structure of 3α,12β-dihydroxy-2β-morpholino-5α-pregnan-20-one,C25H41O4N

The crystal and molecular structure of 3,12-dihydroxy-2-morpholino-5-pregnan-20-one, C₂₅H₄₁O₄N, has been determined:M _r =419.6,P2₁,a=13.5778(8),b=14.4340(8),c=5.8943(5) Å,=94.32(1)°,V _c =1151.9(3) ų,Z=2,D _x =1.21 g cm^–3, (CuK) = 1.5418 Å, =5.6 cm^–1,F(000)=460,R=0.039,R _w =0.040 for 2421 unique observed reflections. All six-membered rings have chair conformations, and theD ring has a 13-envelope conformation. The progesterone side chain has an unusual conformation, and the C16-C17-C20-O20 torsion angle, which defines the conformation, is –152.6(3)°. The unusual conformation seems to be forced by the intramolecular hydrogen bond between the hydroxyl group at C12 and the O20 atom from the side-chain.     

Progress in planar electrochromatography

Developments in planar electrochromatography in open (PEC) and closed (PPEC) systems are reviewed. The discussion focuses on progress in chamber construction for planar electrochromatography, separating system performance, equilibration of the PPEC process, separation time and selectivity, and the general advantages, disadvantages and prospects of this separation mode. Presented at the 11th International Conference on Chemistry and the Environment, 9–12 September 2007, Torum, Poland.     

Spontaneous segregation on a hybrid chiral surface

Segregation of enantiomers in two-dimensional adsorbed layers is a process that is usually controlled by anisotropic directional interactions between adsorbed molecules. In this contribution, we propose a simple theoretical model in which the chiral segregation occurs even though the lateral interactions are neglected. In particular, we consider a solid surface composed of two domains with different patterns of active sites being mirror images of each other. The domains of opposite handedness represent crystal facets of a composite chiral material which are adjoined to form a heterochiral adsorbing surface. To explore equilibrium properties of the system, we use Canonical Ensemble Monte Carlo method for a square lattice. The influence of factors such as energetic properties of the surface and density of the adsorbed layer on the extent of separation is examined. The obtained results indicate that effective two-dimensional separation on the hybrid chiral surface assumed in our model can be achieved only at sufficiently low adsorbate densities. The results also suggest that the segregation on the hybrid surface would be a promising method of enantiodiscrimination for those chiral molecules which do not exhibit strong lateral interactions.     

Structural properties of L-X-L-Met-L-Ala phosphonate tripeptides: a combined FT-IR, FT-RS, and SERS spectroscopy studies and DFT calculations

FT-IR and FT-RS spectra of three phosphonate tripeptides containing P-terminal L-Met-L-Ala [L-Gly-L-Met-L-Ala-PO3H2 (GMA), L-Leu-L-Met-L-Ala-PO3H2 ( LMA), and L-Phe-L-Met-L-Ala-PO3H2 (PMA)] were recorded and analyzed. Vibrational wavenumbers and intensities were calculated by density functional theory (DFT) at the B3LYP/6-311++G** level of theory and compared to these molecules in solid form. On the basis of this comparison, conclusions were drawn about the molecular structures. At the same time, the experimental data served as a test for the computational results. SERS spectra were recorded in a silver colloidal dispersion. Silver colloidal dispersions prepared by simple borohydride reduction of silver nitrate were used as substrates. A comparison is made between the SERS spectra and the spectra of the solid sample. Also, the capability of SERS for spectral fingerprinting of analytes with close structural properties using easily prepared substrates and relatively simple instrumentation is illustrated. By careful analysis, we obtained information on the orientation of these tripeptides and specific-competitive interactions of their functional groups with the silver surface. For example, all molecules are thought to adsorb on a silver surface via a P=O bond and a sulfur atom. In addition, the amide bond of GMA assists in the adsorption process, adopting a tilted orientation on the surface, with the N-H unit being closer to the surface than the C=O moiety. Conversely, the C=O unit of the LMA-CONH- bond lies closer to the silver surface than the N-H moiety. The -CH 3 group and P-O bond of LMA additionally interact with the silver surface, whereas for PMA the L-Phe lies almost flat on the colloidal silver surface.