Molecular dynamics studies on the thermodynamics of supercooled sodium chloride aqueous solution at different concentrations

In this paper we compare recent results obtained by means of molecular dynamics computer simulations on the thermodynamics of TIP4P bulk water and on solutions of sodium chloride in TIP4P water. The concentrations studied are c = 0.67, 1.36 and 2.10 mol kg( - 1). The results are checked against change of water-salt potential and size effects. The systems are studied in a wide range of temperatures, going from ambient temperature to the supercooled region. Analysis of simulated state points, performed on the isochores and on the isotherm plane, allowed the determination of the limit of mechanical stability and of the temperature of maximum density lines. While the presence of ions in the system does not affect the limit of mechanical stability with respect to the bulk, it causes the temperature of the maximum density line to shift to lower pressure and temperature upon increasing concentration. The occurrence of minima in the trend of potential energy as a function of density and the inflections in the low temperature isotherms suggest the presence of liquid-liquid coexistence for bulk water and for the sodium chloride solutions at all concentrations studied.

Parasites of the digestive tract in beef cattle imported from France to Italy

Beef cattle heads (195 heads, 6 batches) imported for fattening from France to Italy were examined. Coprological qualitative and quantitative tests were performed, and the results analysed in relation to sex, breed, age, date of arrival, geographical origin (French department in which the animal was bred), and gathering centre (French department in which the animal was grouped with the others before travelling to Italy). The following parasites were identified: Eimeriidae (overall prevalence 60.5%); Strongyles (59%); Nematodirus spp. (14.3%); Trichuris spp. (4.1%); Capillaria spp. (2.0%); Paramphistomum spp. (27.6%); Dicrocoelium spp. (3.0%); Moniezia spp. (8.7%). All the observed parasites are widely reported in beef cattle either in Italy or in France. However, the seeming absence of Fasciola hepatica was unexpected, as well as the high prevalence of Paramphistomum spp. The variables that appeared to be more linked to parasite epidemiology were sex, altitude of the geographical origin and season.

Resolution and identification of the protein components of the photosystem II antenna system of higher plants by reversed-phase liquid chromatography with electrospray-mass spectrometric detection

Reversed-phase liquid chromatography (RPLC) was interfaced to mass spectrometry (MS) with an electrospray ion (ESI) source for the separation and accurate molecular mass determination of the individual intrinsic membrane proteins that comprise the photosystem II (PS II) major light-harvesting complex (LHC II) and minor (CP24, CP26 and CP29) antenna system, whose molecular masses range between 22,000 and 29,000. PS II is a supramolecular complex intrinsic of the thylacoid membrane, which plays the important role in photosynthesis of capturing solar energy, and transferring it to photochemical reaction centers where energy conversion occurs. The protein components of the PS II major and minor antenna systems were extracted from spinach thylacoid membranes and separated using a butyl-silica column eluted by an acetonitrile gradient in 0.05% (v/v) aqueous trifluoroacetic acid. On-line electrospray MS allowed accurate molecular mass determination and identification of the protein components of PS II major and minor antenna system. The proposed RPLC-ESI-MS method holds several advantages over sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the conventional technique for studying membrane proteins, including a better protein separation, mass accuracy, speed and efficiency.

Buffer additives other than the surfactant sodium dodecyl sulfate for protein separations by capillary electrophoresis

The different compounds utilized as additives to the electrolyte solutions employed in protein capillary zone electrophoresis (CZE) for minimizing protein-capillary wall interactions, for improving selectivity and resolution and for controlling the electroosmotic flow are reviewed. The dependence of the electroosmotic flow on the different variables that can be affected by the incorporation of an additive into the electrolytic solution is discussed. A list of the most effective additives employed for protein separations by CZE is reported in Appendix A.

Capillary electrophoresis of closely related intrinsic thylakoid membrane proteins of the photosystem II light-harvesting complex (LHC II)

The electrophoretic migration behavior of three closely related hydrophobic intrinsic membrane proteins of the photosystem II light-harvesting complex (LHC II) was investigated in free solution capillary electrophoresis at pH 8.0-10 with running electrolyte solutions containing either anionic, zwitter-ionic or nonionic detergents. The complete and repeatable separation of these proteins was accomplished with a running electrolyte solution of 25 mM Tris/192 mM glycine, pH 8.8, containing either sodium dodecyl sulfate or n-octyl beta-D-glucopyranoside at concentration up to 5.0 and 7.0 mM, respectively. Migration times and resolution of the individual LHC II intrinsic membrane proteins were sensitive to the type of detergent. The effect of detergent concentration on the electrophoretic behavior of the LHC II proteins was also investigated. Electroelution of the LHC II components separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to isolate these intrinsic membrane proteins, which were then injected onto the capillary electrophoresis system for peak identification.

Breast cancer patients: long-term relapses

The authors evaluated 200 cases of long-term relapses in patients subjected to mastectomy at least 8 years before and not given any hormonal or other therapy that would have significantly affected the course of the disease. A group of 200 mastectomy patients with early relapses (within 3 years) was used as a control. The following parameters were compared: histologic type, singularity or multiplicity of the relapses at the time of the diagnosis, the patient's age at the time of the mastectomy, the presence of metastatic lymphnodes at the axilla, the clinical course of the disease after the diagnosis of relapse, and the presence of estrogen receptors in the primary tumor. There was a significant higher incidence of lobular histologic type in the group of patients with long-term relapses (p < 0.001). The cases with long-term relapses showed a relatively lower number of relapses in local-region lymphnodes (p < 0.005) a higher number of cases with metastases to the axillary lymphnodes at the time of mastectomy (p < 0.001), a better clinical course (survival) after the diagnosis (mean 3 vs 2.6 years), and more cases with estrogen receptors (p < 0.001) than controls. Premenopausal or postmenopausal status at the time of mastectomy was not significant. After a review of the literature, the authors conclude that relapses that appear after 8 years from the mastectomy occur almost exclusively in patients with a cancer for which the hormonal factor is very important. They hypothesize that even the 18 cases of the series who were without estrogen receptors in reality had receptors saturated by circulating estrogens or receptors for other hormones.

Effect of mobile phase additives on peptide retention in reversed-phase chromatography with pellicular and totally porous sorbents

The effect of two mobile phase additives, trifluoroacetic acid and phosphoric acid, on the energetics of peptide retention in reversed-phase chromatography was investigated using Hy-Tach C18 micropellicular and Vydac C4 and C18 totally porous stationary phases. The effect of the relatively low phase ratio of columns packed with micropellicular sorbents was also examined. The logarithmic retention factors, of two model peptides, Ac-RGGGGLGLGK-amide and Ac-RGAGGLGLGK-amide, were evaluated with different columns and additives in a practical range of eluent strength. The dependence of the logarithmic retention factor on the concentration of acetonitrile in the mobile phase was linear in all cases. The higher sensitivity of the retention to the organic modifier concentration in the case of the Hy-Tach C18 column is attributed to the relatively low phase ratio of this column. Pairwise plots of the logarithmic retention factors were linear. The plots of data obtained with the two additives has unit slopes and thus reveal homoenergetic retention behavior. On the other hand data obtained on two different columns manifest homeoenergetic retention, the slopes of plots are different from unity. The analysis has yielded consistent results and validated the assumption that the retention free energy can be divided into two components arising from mobile phase and stationary phase contributions. The approach also allowed an estimation of the relative phase ratios of the columns and the Vydac C18 column was found to have an 3 and 8 times higher phase ratio than the Vydac C4 and the Hy-Tech C18 column, respectively.

Analysis of epsilon-N-2-furoylmethyl-L-lysine (furosine) in dried milk by capillary electrophoresis with controlled electroosmotic flow using N,N,N',N'-tetramethyl-1,3-butanediamine in the running electrolyte solution

The electrophoresis of epsilon-N-2-furoylmethyl-L-lysine (furosine) was studied in an attempt to develop a method for the identification and quantitation of this compound in processed food. The effect of pH and composition of electrolyte solution on both the electrophoretic migration of furosine and the electroosmotic flow in a bare fused-silica capillary of 75 mu m internal diameter was investigated. We demonstrate that the addition, to the running electrolyte solution, of N,N,N',N'-tetramethyl-1,3-butanediamine (TMBD) at concentrations ranging from 20 to 80 mM improves peak efficiency and can be used to modulate the migration time of furosine by controlling the electroosmotic flow which is reversed from cathodic to anodic. In a sample of dried milk subjected to a long period of storage under controlled conditions, furosine could be efficiently and reproducibly separated and quantitated by employing as the running electrolyte 60 mM TMBD titrated to pH 2.5. Capillary electrophoresis is a promising technique for the rapid identification and quantitation of furosine in processed food.

N,N,N',N'-tetramethyl-1,3-butanediamine as effective running electrolyte additive for efficient electrophoretic separation of basic proteins in bare fused-silica capillaries

The effect of N,N,N',N'-tetramethyl-1,3-butanediamine (TMBD) in the running electrolyte on the electroosmotic flow and the migration behavior of four standard basic proteins in bare fused-silica capillaries was examined at pH 4.0, 5.5, and 6.5. Depending on the electrolyte pH and additive concentration the electroosmotic flow was either cathodic or anodic. A similar Langmuirian-type dependence of the electroosmotic flow on the concentration of TMBD in the running electrolyte was found at the three experimented pH values, which may be indicative of the specific adsorption of the additive in the immobilized region of the electric double layer at the interface between the capillary wall and the electrolyte solution. Electrophoretic separations of the four standard basic proteins performed at the three above pH values, showed well-resolved, efficient and symmetric peaks, demonstrating the utility of this additive for protein electrophoresis in bare fused-silica capillaries. The variations in separation efficiency, peak capacity, resolution and reproducibility of migration times as a function of the additive concentration at pH 6.5 were also examined.

Rapid analysis of somatostatin in pharmaceutical preparations by HPLC with a micropellicular reversed-phase column

A rapid high-performance liquid chromatography method for the analysis of somatostatin in pharmaceutical preparations is described. A commercially available column packed with 2 microns spherical non-porous silica-based reversed-phase sorbent is used, along with a mobile phase consisting of acetonitrile and aqueous phosphoric acid, adjusted to pH 2.8 with sodium hydroxide. The effect of the organic modifier content and column temperature on the retention behaviour of somatostatin is reported. The method is found to be highly selective and specific, as indicated by the baseline separation of a mixture containing somatostatin and two analogue peptides, which differ from the analyte for one and two amino acids, respectively. Down to 10 ng of somatostatin can be detected and the detector response is linear over the concentration range from 4.14 to 20.75 micrograms ml-1. The application of this method to two commercial pharmaceutical formulations of somatostatin is found to give a mean percentage recovery from each of the two commercial samples, subjected to multiple injection analysis (n = 5), of 100.9% with a RSD of 0.92%, and 102.6% with a RSD of 1.56%, respectively.

Combined lectin-affinity and metal-interaction chromatography for the separation of glycophorins by high-performance liquid chromatography

Human erythrocyte sialoglycoproteins, or glycophorins, were chromatographed by lectin-affinity and metal-interaction chromatography on high-performance liquid chromatographic columns. Glycophorins A, B and C were separated from other proteins and from glycophorin E by using a column containing wheat germ agglutinin, immobilized on a microparticulate silica support. The glycophorins were adsorbed on the lectin column from a mobile phase containing 0.25 M sodium chloride and recovered by stepwise desorption with 0.2 M N-acetylglucosamine solution. Glycophorins A, B and C were separated into the individual components on a silica-bound iminodiacetic acid stationary phase in the copper(II) chelate form. The separation of the glycophorins by metal-interaction chromatography was accomplished by decreasing salt gradient elution. Retention times and resolution of the individual glycophorins were sensitive to the initial sodium chloride concentration and the pH of the eluent. Addition of methanol to the eluent increased the resolution. The effects of linear, decreasing gradients of pH and methanol in 25 mM phosphate buffer on the resolution of glycophorins were also investigated. In both types of chromatography the mobile phases contained 0.05% (w/v) sodium dodecyl sulfate. With octylglycoside or CHAPS in the eluent glycophorins A and C could not be eluted. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was used to analyze all the chromatographic results.