Recently, experimental and theoretical studies on the water system are very active and noticeable. A transferable intermolecular potential seven points approach including fluctuation charges and flexible body (ABEEM-7P) based on a combination of the atom-bond electronegativity equalization and molecular mechanics (ABEEM/MM), and its application to small water clusters are explored and tested in this paper. The consistent combination of ABEEM and molecular mechanics (MM) is to take the ABEEM charges of atoms, bonds, and lone-pair electrons into the intermolecular electrostatic interaction term in molecular mechanics. To examine the charge transfer we have used two models coming from the charge constraint types: one is a charge neutrality constraint on whole water system and the other is on each water molecule. Compared with previous water force fields, the ABEEM-7P model has two characters: (1) the ABEEM-7P model not only presents the electrostatic interaction of atoms, bonds and lone-pair electrons and their changing in respond to different ambient environment but also introduces "the hydrogen bond interaction region" in which a new parameter k(lp,H)(R(lp,H)) is used to describe the electrostatic interaction of the lone-pair electron and the hydrogen atom which can form the hydrogen bond; (2) nonrigid but flexible water body permitting the vibration of the bond length and angle is allowed due to the combination of ABEEM and molecular mechanics, and for van der Waals interaction the ABEEM-7P model takes an all atom-atom interaction, i.e., oxygen-oxygen, hydrogen-hydrogen, oxygen-hydrogen interaction into account. The ABEEM-7P model based on ABEEM/MM gives quite accurate predictions for gas-phase state properties of the small water clusters (H(2)O)(n) (n=2-6), such as optimized geometries, monomer dipole moments, vibrational frequencies, and cluster interaction energies. Due to its explicit description of charges and the hydrogen bond, the ABEEM-7P model will be applied to discuss properties of liquid water, ice, aqueous solutions, and biological systems.

A highly enantioselective and practical synthesis of the HIV-1 reverse transcriptase inhibitor efavirenz (1) is described. The synthesis proceeds in 62% overall yield in seven steps from 4-chloroaniline (6) to give efavirenz (1) in excellent chemical and optical purity. A novel, enantioselective addition of Li-cyclopropyl acetylide (4a) to p-methoxybenzyl-protected ketoaniline 3a mediated by (1R,2S)-N-pyrrolidinylnorephedrine lithium alkoxide (5a) establishes the stereogenic center in the target with a remarkable level of stereocontrol.

This paper reports the results of exploratory research on reproductive and sexual health knowledge and sexual behaviour of young, unmarried women who migrate to cities from rural areas for work, and their access to and needs in relation to family planning in Beijing, Guangzhou, Shanghai, Guiyang and Taiyuan, in China. Focus group discussions were conducted with 146 young women aged 16-25 and 58 in-depth interviews with key informants. Some of the young female migrant workers were sexually active and living with their boyfriends, most of whom expected to marry each other. Most of the women lacked basic information about reproduction and contraception, and did not know where or how to obtain contraception. There were social, psychological and economic barriers to accessing services. Only a small proportion of those who were unmarried were using contraception, so induced abortion was often the outcome of unprotected premarital sex. Pleasing male partners also played an important role in unprotected sex. The training, attitudes and approach of the entire family planning service system in relation to unmarried and young people in China, including this migrant population, needs to be reorientated so as to provide them with appropriate and adequate services.

A polarizable force field (PFF) using multiple fluctuating charges per atom, ABEEMσπ PFF, is presented in this work. The fluctuating partial charges are obtained from the electronegativity equalization principle applied to the decomposition scheme of atom-bond regions into multiple charge sites: atomic, lone-pair electron, and σ and π bond regions. These multiple partial charges per atom should better account for the polarization effect than single atomic charge in other PFFs. To evaluate the PFF, structural and energetic properties for some organic and biochemical systems, including rotational barriers; binding energies of base pairs; a base−base interaction in a B-DNA decamer; and interaction energies of ten stationary conformers of a water dimer, peptides, and bases with water molecules, have been calculated and compared with the experimental data or ab initio MP2 results. Molecular dynamics simulations using the PFF have been performed for crambin and BPTI protein systems. Better performances in modeling root-mean-square deviations of backbone bond lengths, bond angles, key dihedral angles, the coordinate root-mean-square shift of atoms, and the distribution of hydrogen bonds have been observed in comparison with other PFFs. These results indicate that the fluctuating charge force field, ABEEMσπ/MM, is accurate and reliable and can be applied to wide ranges of organic and biomolecular systems.

To promote accuracy of the atom-bond electronegativity equalization method (ABEEMσπ) fluctuating charge polarizable force fields, and extend it to include all transition metal atoms, a new parameter, the reference charge is set up in the expression of the total energy potential function. We select over 700 model molecules most of which model metalloprotein molecules that come from Protein Data Bank. We set reference charges for different apparent valence states of transition metals and calibrate the parameters of reference charges, valence state electronegativities, and valence state hardnesses for ABEEMσπ through linear regression and least square method. These parameters can be used to calculate charge distributions of metalloproteins containing transition metal atoms (Sc-Zn, Y-Cd, and Lu-Hg). Compared the results of ABEEMσπ charge distributions with those obtained by ab initio method, the quite good linear correlations of the two kinds of charge distributions are shown. The reason why the STO-3G basis set in Mulliken population analysis for the parameter calibration is specially explained in detail. Furthermore, ABEEMσπ method can also quickly and quite accurately calculate dipole moments of molecules. Molecular dynamics optimizations of five metalloproteins as the examples show that their structures obtained by ABEEMσπ fluctuating charge polarizable force field are very close to the structures optimized by the ab initio MP2/6–311G method. This means that the ABEEMσπ/MM can now be applied to molecular dynamics simulations of systems that contain metalloproteins with good accuracy.