On the collective network of ionic liquid/water mixtures. I. Orientational structure.

In this work, the collective structure of aqueous solutions of ionic liquids was studied by means of molecular dynamics simulations. Various concentrations of 1-butyl-3-methyl-imidazolium tetrafluoroborate and TIP3P water were simulated at the very same size of the simulation box. For the analysis, the ternary system cation/anion/water was subdivided into binary networks. The local structure of each of these six networks is investigated by atom-atom radial distribution functions as well as by the so-called g coefficients, which reveal the mutual orientation of the network constituting partners. Furthermore, the collective structure of the whole samples was characterized by the contribution of each species to the static dielectric constant epsilon(omega=0) and to the Kirkwood G(K) factor. The combination of the analysis tools mentioned above provides knowledge about the cross-linking of the ionic species with the dipolar water. Thereby, the interplay between charge-charge and hydrogen bond networks is analyzed in detail.

Impact of anisotropy on the structure and dynamics of ionic liquids: a computational study of 1-butyl-3-methyl-imidazolium trifluoroacetate.

The complex ionic network of 1-butyl-3-methyl-imidazolium trifluoroacetate was simulated by means of the molecular dynamics methods over a time period of 100 ns. The influence of the anisotropy of the shape and charge distribution of both the cations and the anions on the local (molecular) and global (collective) structure and dynamics is analyzed. The distance-dependent g coefficients of the orientational probability function g(r,Omega) were found to be an excellent way to interpret local structure. Thereby, the combination and interrelation of individual g coefficients elucidate the mutual orientation. Dynamics at the molecular level is characterized by the time correlation function of the center-of-mass corrected molecular dipole moment mucm. Upon uniting the set of molecular dipoles to a single collective rotational dipole moment, MD, dynamics on a global level is studied. Decomposing into subsets of cations and anions respective self terms as well as the prominent cross term can be extracted. This decomposition also enables a detailed peak assignment in dielectric spectra.

Reduced folate carrier-1 80G>A polymorphism affects methotrexate treatment outcome in rheumatoid arthritis.

The folate antagonist methotrexate (MTX) is a drug currently used in the treatment of rheumatoid arthritis (RA). MTX enters the cells through the reduced folate carrier (RFC-1) and is activated to polyglutamates. Previous studies have shown that RFC-1 expression may influence the efficacy of therapy with MTX. The studies suggest that G80A polymorphism in RFC-1 is associated with altered folate/antifolate levels and the subjects carrying homozygous mutant 80AA genotype tend to have higher plasma folate and MTX concentrations and higher erythrocyte polyglutamate levels compared with those with the wild type or heterozygous genotype. It is possible that this polymorphism might influence MTX treatment outcome in patients with RA. In the present study, we examined the association between RFC-1 G80A polymorphism and treatment outcome in patients with RA administered MTX. The study was carried out on 174 patients diagnosed with RA treated with MTX (7.5-15.0 mg weekly) plus low doses of methylprednisone. The RFC-1 80G>A polymorphism (resulting in a histidine-to-arginine substitution at codon 27 of RFC-1) was detected using a polymerase chain reaction-restriction fragment length polymorphism method. The probability of remission of RA symptoms was 3.32-fold higher in carriers of 80AA genotype as compared with patients with 80GG genotype (P=0.021, OR=3.32, 95% CI: 1.26-8.79). The frequency of A allele among MTX responders was 62.1, compared to 47.8% in a group of poor MTX responders (P=0.013, OR=1.78, 95% CI: 1.13-2.81). Moreover, the increase of aminotransferase activity was noted more frequently in carriers of 80AA genotype. The present data suggest that evaluation of RFC-1 gene 80G>A polymorphism may be a useful tool to optimize MTX therapy in patients with RA.

Simulation studies of the protein-water interface. II. Properties at the mesoscopic resolution.

We report molecular dynamics (MD) simulations of three protein-water systems (ubiquitin, apo-calbindin D(9K), and the C-terminal SH2 domain of phospholipase C-gamma1), from which we compute the dielectric properties of the solutions. Since two of the proteins studied have a net charge, we develop the necessary theory to account for the presence of charged species in a form suitable for computer simulations. In order to ensure convergence of the time correlation functions needed for the analysis, the minimum length of the MD simulations was 20 ns. The system sizes (box length, number of waters) were chosen so that the resulting protein concentrations are comparable to experimental conditions. A dielectric component analysis was carried out to analyze the contributions from protein and water to the frequency-dependent dielectric susceptibility chi(omega) of the solutions. Additionally, an even finer decomposition into protein, two solvation shells, and the remaining water (bulk water) was carried out. The results of these dielectric decompositions were used to study protein solvation at mesoscopic resolution, i.e., in terms of protein, first and second solvation layers, and bulk water. This study, therefore, complements the structural and dynamical analyses at molecular resolution that are presented in the companion paper. The dielectric component contributions from the second shell and bulk water are very similar in all three systems. We find that the proteins influence the dielectric properties of water even beyond the second solvation shell, in agreement with what was observed for the mean residence times of water molecules in protein solutions. By contrast, the protein contributions, as well as the contributions of the first solvation shell, are system specific. Most importantly, the protein and the first water shell around ubiquitin and apo-calbindin are anticorrelated, whereas the first water shell around the SH2 domain is positively correlated.

Simulation studies of the protein-water interface. I. Properties at the molecular resolution.

We report molecular dynamics simulations of three globular proteins: ubiquitin, apo-calbindin D(9K), and the C-terminal SH2 domain of phospholipase C-gamma1 in explicit water. The proteins differ in their overall charge and fold type and were chosen to represent to some degree the structural variability found in medium-sized proteins. The length of each simulation was at least 15 ns, and larger than usual solvent boxes were used. We computed radial distribution functions, as well as orientational correlation functions about the surface residues. Two solvent shells could be clearly discerned about charged and polar amino acids. Near apolar amino acids the water density near such residues was almost devoid of structure. The mean residence time of water molecules was determined for water shells about the full protein, as well as for water layers about individual amino acids. In the dynamic properties, two solvent shells could be characterized as well. However, by comparison to simulations of pure water it could be shown that the influence of the protein reaches beyond 6 A, i.e., beyond the first two shells. In the first shell (r < or =3.5 A), the structural and dynamical properties of solvent waters varied considerably and depended primarily on the physicochemical properties of the closest amino acid side chain, with which the waters interact. By contrast, the solvent properties seem not to depend on the specifics of the protein studied (such as the net charge) or on the secondary structure element in which an amino acid is located. While differing considerably from the neat liquid, the properties of waters in the second solvation shell (3.5< r < or =6 A) are rather uniform; a direct influence from surface amino acids are already mostly shielded.

Simulation studies of ionic liquids: orientational correlations and static dielectric properties.

The ionic liquids BMIM+I-, BMIM+BF4-, and BMIM+PF6- were simulated by means of the molecular dynamics method over a time period of more than 100 ns. Besides the common structural analysis, e.g., radial distribution functions and three dimensional occupancy plots, a more sophisticated orientational analysis was performed. The angular correlation functions g(00)110(r) and g(00)101(r) are the first distance dependent coefficients of the pairwise orientational distribution function g(rij,Omega1,Omega2,Omega12). These functions help to interpret the three dimensional plot and reveal interesting insights into the local structure of the analyzed ionic liquids. Furthermore, the collective network of ionic liquids can be characterized by the Kirkwood factor Gkappa(r) [J. Chem. Phys. 7, 911 (1939)]. The short-range behavior (r<10 A) of this factor may be suitable to predict the water miscibility of the ionic liquid. The long-range limit of Gkinfinity is below 1 which demonstrates the strongly coupled nature of the ionic liquid networks. In addition, this factor relates the orientational structure and the dielectric properties of the ionic liquids. The static dielectric constant epsilon(omega=0) for the simulated system is 8.9-9.5. Since in ionic liquids the very same molecule contributes to the total dipole moment as well as carries a net charge, a small, but significant contribution of the cross term between the total dipole moment and the electric current to epsilon(omega=0) is observed.

International Commission for Protection against Environmental Mutagens and Carcinogens. ICPEMC Working Paper No. 10. A new approach to germinal mutation surveillance: pair-wise evaluation of component elements in unidentified multiple congenital abnormalities.

In the Hungarian population-based surveillance of germinal mutations, 3 indicator conditions of offspring are being followed, namely 15 sentinel anomalies, Down syndrome and unidentified multiple congenital abnormality. The latter is discussed here as a possible indicator of germinal dominant gene and chromosomal mutations. The component congenital abnormalities of unidentified multiple congenital abnormalities are classified into 45 groups. The component congenital abnormalities were reduced to pairs. A pair is a set of 2 independent component congenital abnormalities in index patients with 2 or more congenital abnormalities. Baseline figures of all component congenital abnormality pairs in 3722 unidentified multiple congenital abnormalities were determined in the study period 1973-1982. The observed data for 1983 were compared with expected occurrences based on baseline figures. This pair-wise evaluation of component elements within unidentified multiple congenital abnormalities seems to be an adequate surveillance method to detect any time cluster of congenital abnormality pairs due to environmental factors including germinal mutagens.

The load of genetic and partially genetic diseases in man. II. Some selected common multifactorial diseases: estimates of population prevalence and of detriment in terms of years of lost and impaired life.

This paper presents epidemiological data on the prevalence of 26 common (i.e., having a lifetime prevalence of more than 1 per 10(4) individuals in the population) multifactorial diseases in Hungary and estimates of detriment associated with them. The detriment is expressed using 3 indicators, namely years of lost life (LL), potentially impaired life (PIL) and actually impaired life (AIL). The total prevalence of these diseases in Hungary has been estimated to be about 6500 per 10(4) individuals in the population. This estimate is in agreement with published data for other parts of the world. On the basis of clinical severity, these diseases have been split into 3 groups, namely (1) very severe (schizophrenia, multiple sclerosis, epilepsy, acute myocardial infarction and related conditions, and systemic lupus erythematosus); (2) moderately severe and/or episodal or seasonal (15 entities including Graves' disease, diabetes mellitus, gout, affective psychoses, essential hypertension, peptic ulcers, asthma, etc.); and (3) less severe than those in the first 2 groups (varicose veins, allergic rhinitis, atopic dermatitis, Scheuermann disease and adolescent idiopathic scoliosis). The essential clinical and genetic aspects of these diseases are briefly discussed. With the exception of epilepsy, none of the diseases included in our list causes mortality between ages 0 and 19. However, they are among the leading causes of death between ages 20 and 69 and thereafter. A sizeable proportion of those with essential hypertension, diabetes mellitus, rheumatoid arthritis, etc. survive to 70 years and beyond, as do those with gout, glaucoma, allergic rhinitis, psoriasis, etc. Overall, about 16% of all deaths that occur in Hungary every year (all age groups) can be attributed to these diseases. The mean number of years of PIL covers a wide range (about 20-40, 12-70 and 40-60 for groups 1, 2 and 3, respectively), the overall mean being about 24 years. However, the nature and degree of impairment and the impact on the life quality of those afflicted differ for the different diseases. Likewise, the mean number of years of AIL (for which the interval between the mean age at premature retirement and mean age at death was used as a rough index) also spans a wide range from 16 to 45, and the overall mean is about 20 years. At the population level, the diseases considered in this paper cause about 2700 years of LL, 96,000 years of PIL and about 5800 years of AIL per 10(4) individuals in the population. Relative to Mendelian diseases as a whole, these multifactorial diseases are associated with much greater detriment (LL: 1.4 X; PIL: 30 X and AIL: 3.9 X).

A semiquantitative score system for epidemiologic studies of fetal alcohol syndrome.

A total of 464 children of 323 women registered for alcoholism treatment in Budapest, Hungary, were studied in 1977-1979. A complex epidemiologic investigation was carried out using medical, psychological and anthropological data. The data were evaluated on the basis of a semiquantitative diagnostic scoring system for fetal alcohol syndrome. The score distribution curve for 301 children whose mothers imbibed during pregnancy was statistically significantly different from the score distribution curve for 163 children born to alcoholic mothers who remained abstinent during pregnancy and from the curve for a matched control group of 464 children. A significant difference was also found between the score distribution curves for the latter two groups. Twenty-five children of 301 drinkers (8.3%) scored below -30 points and were said to show typical manifestations of the syndrome. All of the mothers in this group imbibed large amounts of alcohol during pregnancy. A further 205 children of 464 alcoholic mothers (44.2%) scored between -30 and -10 points and were diagnosed as having an atypical form of the syndrome. Among the 205 children, 168 were the offspring of 301 drinkers (55.8%) and 37 were the offspring of 163 alcoholic females who were abstinent during pregnancy (22.7%). A stepwise discriminant analysis showed the best discriminating variables--in order of entry into the discriminant functions--to be current weight, nose-upper lip distance, behavioral disturbance (irritability), root of the nose, intelligence quotient, and palpebral fissure. The most important cause of fetal alcohol syndrome is the direct toxic effect of alcohol on the fetus.