Mimicking the biomolecular control of calcium oxalate monohydrate crystal growth: effect of contiguous glutamic acids

Scanning confocal interference microscopy (SCIM) and molecular dynamics (MD) simulations were used to investigate the adsorption of the synthetic polypeptide poly(l-glutamic acid) (poly-glu) to calcium oxalate monohydrate (COM) crystals and its effect on COM formation. At low concentrations (1 μg/mL), poly-glu inhibits growth most effectively in ?001? directions, indicating strong interactions of the polypeptide with {121} crystal faces. Growth in ?010? directions was inhibited only marginally by 1 μg/mL poly-glu, while growth in ?100? directions did not appear to be affected. This suggests that, at low concentrations, poly-glu inhibits lattice-ion addition to the faces of COM in the order {121} > {010} ≥ {100}. At high concentrations (6 μg/mL), poly-glu resulted in the formation of dumbbell-shaped crystals featuring concave troughs on the {100} faces. The effects on crystal growth indicate that, at high concentrations, poly-glu interacts with the faces of COM in the order {100} > {121} > {010}. This mirrors MD simulations, which predicted that poly-glu will adsorb to a {100} terrace plane (most calcium-rich) in preference to a {121} (oblique) riser plane but will adsorb to {121} riser plane in preference to an {010} terrace plane (least calcium-rich). The effects of different poly-glu concentration on COM growth (1-6 μg/mL) may be due to variations between the faces in terms of growth mechanism and/or (nano)roughness, which can affect surface energy. In addition, 1 μg/mL might not be adequate to reach the critical concentration for poly-glu to significantly pin step movement on {100} and {010} faces. Understanding the mechanisms involved in these processes is essential for the development of agents to reduce recurrence of kidney stone disease.     

Quantifying uncertainty in determination of polysaccharides in glycoconjugate vaccines based on in-house validation data

The measurement uncertainty in quantifying polysaccharides in glycoconjugate vaccines was estimated in order to ascertain compliance of these products in the batch release procedure of an Official Medicines Control Laboratory. A single-laboratory validation approach of an internal analytical procedure to quantify the total saccharide by the way of the sialic acid (N-Acetylneuraminic acid) concentration in a meningococcal glycoconjugate vaccine by High Performance Anion Exchange Chromatography coupled with Pulsed Amperometric Detection is reported. Uncertainty components from precision, bias and other sources were evaluated. It turned out that uncertainty is dominated by the precision contribution, while bias was mainly due to the non-recovery from hydrolysis. As a consequence, a correction factor was considered. At a confidence level of approximately 95%, the expanded uncertainty of the total polysaccharide concentration in a vaccine, when measured using the internal method, was found to be 11.5%.     

Solvent free oxidation of primary alcohols and diols using thymine iron(III) catalyst

In this study, we developed an efficient and selective iron-based catalyst system for the synthesis of ketones from secondary alcohols and carboxylic acids from primary alcohol. In situ generated iron catalyst of thymine-1-acetate (THA) and FeCl(3) under solvent-free condition exhibits high activity. As an example, 1-octanol and 2-octanol were oxidized to 1-octanoic acid and 2-octanone with 89% and 98% yields respectively.     

Validation of a fast screening method for the detection of cocaine in hair by MALDI-MS

The sensitivity and specificity of a novel method of screening for cocaine in hair, based on matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry (MS), have been evaluated. The method entails a rapid extraction procedure consisting of shaking 2.5 mg pulverised hair at high frequency in the presence of an acidic solution (160 μL of water, 20 μL of acetonitrile and 20 μL of 1 M trifluoroacetic acid) and a stainless-steel bullet. Following centrifugation, the supernatant is dried under a nitrogen stream, and the residue is reconstituted in 10 μL of methanol/trifluoroacetic acid (7:3; v/v). One microlitre of the extract is deposed on a MALDI sample holder previously scrubbed with graphite; an α-cyano-4-hydroxycinnamic acid (matrix) solution is electrosprayed over the dried sample surface to achieve a uniform distribution of matrix crystals. The identification of cocaine is obtained by post-source decay experiments performed on its MH⁺ ion (m/z 304), with a limit of detection of 0.1 ng/mg of cocaine. A total of 304 hair samples were analysed in parallel by MALDI-MS and a reference gas chromatography-MS method. The obtained results demonstrate specificity and sensitivity of 100% for MALDI-MS. Evidence of cocaine presence was easily obtained even when hair samples exhibiting particularly low cocaine levels (<0.5 ng/mg) were analysed.     

Graph realizations associated with minimizing the maximum eigenvalue of the Laplacian

In analogy to the absolute algebraic connectivity of Fiedler, we study the problem of minimizing the maximum eigenvalue of the Laplacian of a graph by redistributing the edge weights. Via semidefinite duality this leads to a graph realization problem in which nodes should be placed as close as possible to the origin while adjacent nodes must keep a distance of at least one. We prove three main results for a slightly generalized form of this embedding problem. First, given a set of vertices partitioning the graph into several or just one part, the barycenter of each part is embedded on the same side of the affine hull of the set as the origin. Second, there is an optimal realization of dimension at most the tree-width of the graph plus one and this bound is best possible in general. Finally, bipartite graphs possess a one dimensional optimal embedding.     

Heterolytic dihydrogen activation by B(C6F5)3 and carbonyl compounds

Aromatic carbonyl compounds in combination with B(C(6)F(5))(3) are able to activate H(2) heterolytically. The reactivity of the carbonyl-B(C(6)F(5))(3) adduct is initiated by its thermal dissociation into components. After H(2) addition, aromatic carbonyl compounds convert into aryl-substituted methanes or alcohols.     

Prevalence of voice symptoms and risk factors in teacher students

Teacher students seem to have low awareness of the vocal demands in their future professions, and students with vocal symptoms are at risk for developing voice disorders during their professional careers. The purpose of the present study was to determine the prevalence of voice problems in teacher students at the very beginning of their education at the university. Of 1636 students approached in the first couple of days, 1250 (76%) answered two questionnaires about voice symptoms, Screen6 and Swedish Voice Handicap Index (Sw-VHI), and one questionnaire about potential risk factors. A majority of the students were women, and their mean age was 23 years (range, 18-52 years). The results showed that 208 of 1250 students (17%) had voice problems, defined as at least two symptoms weekly or more often in Screen6. The proportion of women was larger in the group with voice problems than in the group without voice problems. Significant risk factors for voice problems were vocal fold problems in childhood and adulthood, frequent throat infections, airborne allergy, smoking, hearing problems, previous work as teacher or leader, voice demanding hobbies, and previous speech therapy or voice training. There was a clear association between the number of potential vocal risk factors and the number of voice symptoms. There was also a strong association between the scores of the two questionnaires, the Sw-VHI and the Screen6. Students with voice problems according to Screen6 scored 23.1 (mean Sw-VHI) compared with 7.8 for students without voice problems.