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To understand the microsolvation of alkaline-earth dihalides in water and provide information about the dependence of solvation processes on different halides, we investigated CaBr

In order to understand the hydration processes of BaCl

Integrated tempering sampling (ITS) method is an approach to enhance the sampling over a broad range of energies and temperatures in computer simulations. In this paper, a new version of integrated tempering sampling method is proposed. In the new approach presented here, we obtain parameters such as the set of temperatures and the corresponding weighting factors from canonical average of potential energies. These parameters can be easily obtained without estimating partition functions. We apply this new approach to study the Lennard–Jones fluid, the ALA-PRO peptide and the single polymer chain systems to validate and benchmark the method.

There are sex differences in some brain areas in mammalians. Parkinson's disease (PD), caused by the mesencephalic substantia nigra (SN) dopaminergic neuronal loss, displays sexual difference, i.e., the incidence is higher and the symptoms are more intense in males than that in females. However, it has not been known whether sexual dimorphisms exist in the SN. Sixty adult Sprague-Dawley rats were randomly divided into 5 groups: (1) Female intact group (F-INT group); (2) Male intact group (M-INT group); (3) Ovariectomized group (OVX group); (4) Castration group (CAST group); (5) Ovariectomized + estrogen-replaced group (OVX-E(2) group): The rats received sequentially physiological dose of estrogen for 3 d from the 7th day after ovariectomization. P50 auditory evoked potential (P50) was recorded for 14 d from electrodes inserted in the rat right SN in quiet and awake state. After recording, the brain tissues were dissected and the tyrosine hydroxylase (TH)-expressing neurons in the compact zone of the SN were counted using immunohistochemical method. The results showed that the number of TH-positive (TH(+)) cells in the SN of normal male animals was less than that in normal female rats (P0.05), and the T/C ratio of P50 in normal males was significantly less than that in normal females (P0.01), indicating that there exists sexual difference in function and structure in the SN. No differences in the T/C ratio of P50 or the number of TH(+) cells were found between M-INT and CAST groups. The T/C ratio of P50 and the number of TH(+) cells in the SN in OVX group were reduced significantly compared with those in F-INT group (P0.01). There was no significant difference in the T/C ratio of P50 and the number of TH(+) cells in the SN between OVX- E(2) and F-INT groups 15-20 d after estrogen replacement, suggesting that estrogen can promote the survival and functional recovery of dopaminergic neurons in the SN. The results suggest that there exist sex-specific differences in the dopaminergic neurons in the SN structurally and functionally. The difference of estrogen level in cerebra between male and female animals may account for the sexual differences. Endogenous estrogen plays an important role in maintaining the integrity and modulating the functional activity of dopamine system in the SN.

Using optical tweezers, here we show that the overstretching transition force of double-stranded DNA (dsDNA) is lowered significantly by the addition of the disaccharide trehalose as well as certain polyol osmolytes. This effect is found to depend linearly on the logarithm of the trehalose concentration. We propose an entropic driving mechanism for the experimentally observed destabilization of dsDNA that is rooted in the higher affinity of the DNA bases for trehalose than for water, which promotes base exposure and DNA melting. Molecular dynamics simulation reveals the direct interaction of trehalose with nucleobases. Experiments with other osmolytes confirm that the extent of dsDNA destabilization is governed by the ratio between polar and apolar fractions of an osmolyte.