Nanoscale organization of adsorbed collagen: influence of substrate hydrophobicity and adsorption time

The adsorption of collagen on polystyrene (PS) and polystyrene oxidized by oxygen plasma discharge (PSox) was studied as a function of time using radiolabeling, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Radiolabeling and XPS indicated that the initial step of adsorption was faster on PS than on PSox. AFM imaging under water revealed very different supramolecular organization of the adsorbed films depending on time and on the nature of the substrate: PS showed patterns of collagen aggregates at all adsorption times (from 1 min to 24 h); PSox was covered with a smooth layer except at long adsorption times (24 h), for which a mesh of collagen structures was observed. After fast drying, the collagen layer remained continuous and showed a morphology which recalled that observed under water. The mechanical stability of the adsorbed films was assessed under water by scraping with the AFM probe at different loading forces: no perturbations were created on PSox; in contrast, the layer adsorbed on PS was sensitive to scraping, the minimum force required to alter the collagen layer morphology increasing with time. These differences in the film properties were correlated with force measurements upon retraction: multiple adhesion forces were observed with collagen adsorbed on PS samples, whereas such an effect was never observed on PSox. The results show that the amount adsorbed and the organization of the adsorbed film respond differently to the adsorption time and that this is influenced by surface hydrophobicity. The quick initial adsorption on PS, compared to PSox, is thought to leave dangling collagen segments that are responsible for the observed morphology, for adhesion forces, and for lower mechanical resistance of the adsorbed layer.     

Synthesis and Crystal Structure of 1-（4-Chlorophenyl）-2-cyano-3-amino-3a-hydroxy-3a,3b ,6, 7-te trah y drobenzo[ 4,5]indene

1 INTRODUCTION dimerization of α,β-unsaturated ketones[10]. Herein we discuss the crystal structure of the title compound In the early seventies three groups of investiga- synthesized by the reaction of 2-cyano-3-(4-chloro- tors[1~3] have established that low-valent titanium phenyl)-3-(1-tetralon-2-yl) induced by TiCl4/Zn system. can abstract oxygen from ketones or aldehydes, lead- When 2-cyano-3-(4-chlorophenyl)-3-(1-tetra- lon-2-yl) ing to the formation of olefins. A variety of other…     

Online trace enrichment to determine pyrethroids in river water by HPLC with column switching and photochemical induced fluorescence detection

The potential of online trace enrichment on a highly apolar short column in LC was evaluated for the determination of pyrethroids in river water. Twelve millilitres of water samples, modified with 8 mL ACN (ACN/water 40:60, v/v), were passed through 50 x 4.6 mm ID first separation column packed with 5 microm Hypersil Elite C18. Pesticides were preconcentrated in this column while the matrix background was eluted to waste. Separation of pesticides was performed on a 3.5 microm symmetric C18 column (250 x 4.6 mm ID) with an ACN step gradient as mobile phase and fluorescence detection was used after postcolumn derivatization by using UV light. The use of photochemically induced fluorescence for detection improved sensitivity and selectivity. Quantification limits ranged from 0.05 to 0.1 microg/L and pesticide recoveries at two concentration levels (0.1 and 0.5 microg/L) were between 93.1 and 118.6%, with RSD between 2.5 and 7.5% (n = 3) in river water samples. No matrix effect was detected.     

Synthesis and Crystal Structure of 1-(N,N-Di-(p-toluenesulfonyl))-amino-2-(N'-p-toluenesulfonyl)-amino-3,5-dinitrobenzene

The title compound,1-(N,N-di-(p-toluenesulfonyl))-amino-2-(N'-p-toluenesulfonyl)-amino-3,5-dinitrobenzene,was synthesized and structurally determined by single-crystal X-ray diffraction method. It crystallizes in orthorhombic,space group Pna21 with a=13.723(2),b=25.354(4),c=8.6565(12) ,V=3011.9(8) 3,Z=4,Mr=660.68,F(000)=1368,Dc=1.457 g/cm3,μ=0.309,the final R=0.0609 and wR=0.1042. The H atom of N2-H group,which is the unique recognition site to anion,is enveloped by two oxygen atoms and one benzene from two and one p-toluenesulfonyl moieties,respectively.     

Mass spectrometric study of tricarbonyl (eta(6)-phenyl methanols) of chromium(0)

A mass spectrometric study of several tricarbonyl (eta(6)-phenyl methanols) of chromium(0) was performed. Electron ionization (EI), chemical ionization (CI) and fast atom bombardment (FAB) mass spectra were acquired for each molecule, and compared in order to establish a general fragmentation pattern. The suggested pathways were investigated and confirmed by means of constant b/e linked scans and high resolution data. In addition a Hammett-McLafferty correlation for some peaks derived from the molecular ions was accomplished.     

Synthesis of bioactive sesterterpenolides from ent-halimic acid. 15-epi-ent-Cladocoran A and B

The bioactive sesterterpenoid gamma-hydroxybutenolides 15,18-bisepi-ent-Cladocoran A and B, 1 and 2, and 15-epi-ent-Cladocoran A and B, 57 and 55, were synthesized from ent-halimic acid. The synthesized sesterterpenolids 2, 55, 57, and 59 inhibited cellular proliferation (IC(50) congruent with 2 micro M) of a number of human leukaemic and solid tumor cell lines.     

Synthesis and Diels-Alder Reactions of a New Kind of Chiral Dienophiles: Cyclic Vinyl-p-tolylsulfilimines

A new kind of chiral dienophiles, cyclic vinyl-p-tolylsulfilimines (2a and 2b), were obtained from the corresponding (Z)-sulfinylacrylonitriles with HBF(4) and methanol. The asymmetric Diels-Alder reaction of optically pure 2a with cyclopentadiene under mild thermal or catalyzed conditions afforded only the endo-4a adduct with complete endo and pi-facial selectivities. The ability of the sulfilimine moiety to enhance the dienophilic reactivity of the double bond is similar to that of the sulfinyl group.     

Adsorptive stripping behaviour of mitoxantrone on carbon paste electrodes

The electrooxidation of mitoxantrone (MXT) on carbon paste electrodes was studied using voltammetric techniques in adsorption conditions. The analyte was accumulated at the working electrode (a carbon paste electrode) under precisely controlled mass-transport conditions and stripped electrochemically in the same solution. An electrode pretreatment is proposed which shows good reproducibility of the analytical signal (0.81%). The stripping step was studied with alternating current voltammetry providing a linear response in the concentration range 5 x 10(-11) to 7 x 10(-10)M in aqueous samples. Finally, a method using the medium exchange and AC phase-selective adsorptive stripping voltammetry technique was proposed for MXT analysis in urine samples.     

New Fischer carbene complexes of rhodium(i): preparation and 2-cyclopentenone ring synthesis by annelation to alkynes

A new type of metal carbene complexes of group 9, specifically a cationic Fischer carbene of rhodium(I), has been synthesized from chromium carbene complexes via double transfer of carbene and CO ligands. These complexes reveal a different reactivity than other transition metal carbenes, including their chromium precursors, toward neutral and electron-poor alkynes, giving selectively polysubstituted cyclopentenones.     

Testing green coffee for ochratoxin A, part I: estimation of variance components

The variability associated with testing lots of green coffee beans for ochratoxin A (OTA) was investigated. Twenty-five lots of green coffee were tested for OTA contamination. The total variance associated with testing green coffee was estimated and partitioned into sampling, sample preparation, and analytical variances. All variances increased with an increase in OTA concentration. Using regression analysis, mathematical expressions were developed to model the relationship between OTA concentration and the total, sampling, sample preparation, and analytical variances. The expressions for these relationships were used to estimate the variance for any sample size, subsample size, and number of analyses for a specific OTA concentration. Testing a lot with 5 microg/kg OTA using a 1 kg sample, Romer RAS mill, 25 g subsamples, and liquid chromatography analysis, the total, sampling, sample preparation, and analytical variances were 10.75 (coefficient of variation [CV] = 65.6%), 7.80 (CV = 55.8%), 2.84 (CV = 33.7%), and 0.11 (CV = 6.6%), respectively. The total variance for sampling, sample preparation, and analytical were 73, 26, and 1%, respectively.