No abstract

No abstract

Multiple sclerosis (MS) is a nervous system disease that affects the fatty myelin sheaths around the axons of the brain and spinal cord, leading to demyelination and a broad range of signs and symptoms. MS can be difficult to diagnose because its signs and symptoms may be similar to other medical problems. To find out which metabolites in serum are effective for the diagnosis of MS, we utilized metabolic profiling using proton nuclear magnetic resonance spectroscopy ((1)H-NMR). Random forest (RF) was used to classify the MS patients and healthy subjects. Atomic absorption spectroscopy was used to measure the serum levels of selenium. The results showed that the levels of selenium were lower in the MS group, when compared with the control group. RF was used to identify the metabolites that caused selenium changes in people with MS by building a correlation model between these metabolites and serum levels of selenium. For the external test set, the obtained classification model showed a 93% correct classification of MS and healthy subjects. The regression model of levels of selenium and metabolites showed the correlation (R(2)) value of 0.88 for the external test set. The results indicate the suitability of NMR as a screen for identifying MS patients and healthy subjects. A novel model with good prediction outcomes was constructed between serum levels of selenium and NMR data.

No abstract

We employ reverse nonequilibrium molecular dynamics simulations to investigate the interfacial heat transfer in composites formed by an ungrafted or a grafted carbon nanotube which is surrounded by oligomeric polyamide-6,6 chains. The structural properties of the polymer matrix and the grafted chains are also studied. The influence of the grafting density, the length of the grafted chains as well as their chemical composition on the interfacial thermal conductivity (λi) are in the focus of our computational study. For the considered grafted polyethylene and polyamide chains we do not find a sizeable difference in the observed λi values. In contrast to this insensitivity, we predict a rather strong influence on λi by the grafting density and the length of the grafted chains. This dependence is an outcome of modifications in the structural properties of the polymer matrix as well as the grafted chains. Functionalization of the nanotube has a sizeable influence on the interfacial thermal conductivity. Its enhancement is caused by the chemical bonds between the nanotube and grafted chain atoms which reduce the number of Kapitza resistances hindering the heat transfer in polymer samples. The phonon density of states profiles confined to the bonded nanotube and the grafted chain atoms are used to emphasize the phonon support of the thermal conductivity in nanocomposites with grafted tubes. Strategies to tailor nanotube containing composites with higher thermal conductivities than that realized in the bare polymer are shortly touched.

Background. Colorectal carcinoma is the third cause of cancer deaths in the world. For diagnosis, invasive methods like colonoscopy and sigmoidoscopy are used, and noninvasive screening tests are not very accurate. We decided to study the potential of 1HNMR spectroscopy with metabolomics and chemometrics as a preliminary noninvasive test. We obtained a distinguishing pattern of metabolites and metabolic pathways between colon cancer patient and normal. Methods. Sera were obtained from confirmed colon cancer patients and the same number of healthy controls. Samples were sent for 1HNMR spectroscopy and analysis was carried out Chenomex and MATLAB software. Metabolites were identified using Human Metabolic Data Base (HDMB) and the main metabolic cycles were identified using Metaboanalyst software. Results. 15 metabolites were identified such as pyridoxine, orotidine, and taurocholic acid. Main metabolic cycles involved were the bile acid biosynthesis, vitamin B6 metabolism, methane metabolism, and glutathione metabolism. Discussion. The main detected metabolic cycles were also reported earlier in different cancers. Our observations corroborated earlier studies that suggest the importance of lowering serum LCA/DCA and increasing vitamin B6 intake to help prevent colon cancer. This work can be looked upon as a preliminary step in using 1HNMR analysis as a screening test before invasive procedures.

The most stable conformer has the //-ethyl group syn to the carbonyl, except for X = H where it is anti to the carbonyl. Activation free energies AG*29s in kcal mol-1 (gas/solution) are 16.4 (0.1)/18.2 (0.1) for X = CF3 (in CCL,), 15.4 (0.2)/18.5 (0.2) for X = CH3 (in DMSO-t/6), and 19.6 (0.2)/21.0 (0.2) for X = H (in DMSO-i/e). Gas-phase values of AG*298 are lower the liquid-phase values by 1.4-3.1 kcal mol-1. This is consistent with previous experimental studies.

The performance of the ab initio and density functional theory (DFT) functional, B3LYP and PBEPBE, in conjunction with selected basis sets for the prediction of 31 P shielding constants for small phosphorous-containing molecules is assessed. The effects of applied factors are discussed. By including the electron correlation treatment, B3LYP and PBEPBE are the most accurate methods to compute the chemical shielding for a set of small phosphines that was studied. Also, additional improvements of DFT were obtained by empirical scaling of basis sets in calculation of chemical shifts. For molecules containing only phosphorous and carbon atoms with sp 3 hybridization, the PBEPBE/6-311G(d,p) level of theory has been shown to provide reliable 31 P chemical shifts.