Laser desorption VUV postionization MS imaging of a cocultured biofilm

Laser desorption postionization mass spectrometry (LDPI-MS) imaging is demonstrated with a 10.5 eV photon energy source for analysis and imaging of small endogenous molecules within intact biofilms. Biofilm consortia comprised of a synthetic Escherichia coli K12 coculture engineered for syntrophic metabolite exchange are grown on membranes and then used to test LDPI-MS analysis and imaging. Both E. coli strains displayed many similar peaks in LDPI-MS up to m/z 650, although some observed differences in peak intensities were consistent with the appearance of byproducts preferentially expressed by one strain. The relatively low mass resolution and accuracy of this specific LDPI-MS instrument prevented definitive assignment of species to peaks, but strategies are discussed to overcome this shortcoming. The results are also discussed in terms of desorption and ionization issues related to the use of 10.5 eV single-photon ionization, with control experiments providing additional mechanistic information. Finally, 10.5 eV LDPI-MS was able to collect ion images from intact, electrically insulating biofilms at ～100 μm spatial resolution. Spatial resolution of ～20 μm was possible, although a relatively long acquisition time resulted from the 10 Hz repetition rate of the single-photon ionization source.

An on‐line sample pretreatment technique for the HPLC analysis of plant samples

A continuous‐flow, on‐line sample pretreatment technique using a silica gel microsyringe extractor has been developed. All steps including extraction, separation, clean‐up, and concentration occur in the microsyringe. The overall sample pretreatment process takes <10 min per sample. Different polarity chemicals in the plant sample are successively extracted and separated, and analyzed in parallel using HPLC–UV and HPLC–UV–MS/MS. Polycyclic aromatic hydrocarbons, alkylphenols, and plant hormones were determined as model compounds for nonpolar, intermediate polarity, and polar fractions, respectively. All the parameters that influence the extraction and separation efficiency of the microsyringe extractor have been optimized and evaluated. Under the optimized conditions, recoveries of target compounds ranged from 78.4 to 101.9%, the RSD was <12.8% and the square of the correlation coefficient was >0.99. Complex plant samples of Sambucus Mandshurica Kitag have been tested using this method. Fluorene, phenanthrene, pyrene, and plant hormones were detected in all the samples, and concentrations ranged from 24.2–34.9, 43.8–67.1, 25.9–29.2, and 14.5～110.8 ng/g, respectively.     

A rapid and convenient method for preparative separation of three indissolvable polyphenols from Euphorbia pekinensis by the flexible application of solvent extraction combined with counter‐current chromatography

A rapid and convenient method was established to preparatively isolate the three ellagic acid types of compounds, which were the main polyphenols in Euphorbia pekinensis, by flexibly applying solvent extraction combined with counter‐current chromatography (CCC). The total extract (extracted using 95% ethanol) of E. pekinensis was pretreated by two simple steps before CCC isolation, following the procedure: the total extract was extracted by classical solvent extraction using petroleum ether and ethyl acetate, respectively, and then the ethyl acetate extract was suspended using 95% ethanol, after being allowed to stand overnight, the sediment was obtained. Partial sediment (100 mg) was then directly separated by CCC with a two‐phase solvent system composed of chloroform‐95% ethanol‐water‐85% formic acid (50:50:50:5, v/v/v/v). About 22 mg of 3,3′‐dimethoxy ellagic acid (1), 12 mg of 3,3′‐di‐O‐methyl‐4‐O‐(β‐d ‐xylopyranosyl)ellagic acid (2), and 35 mg of ellagic acid (3) with purities of 96.0, 95.2, and 95.4% were obtained respectively in one step within 4 h. After being purified by washing with methanol, the purities of the three compounds obtained were all above 98%. The purities were determined by HPLC and their chemical structures were further identified by ¹H and ¹³C NMR spectroscopy. The recoveries were calculated as 84.6, 85.7, and 89.5%, respectively. The result demonstrated that the present isolation method was rapid, economical and efficient for the preparative separation of polyphenols from E. pekinensis.     

Non-phospholipid liposomes with high sterol content display a very limited permeability

We demonstrate that it is possible to form non-phospholipid fluid bilayers in aqueous milieu with a mixture of palmitic acid (PA),cholesterol (Chol),and cholesterol sulfate (Schol) in a molar proportion of 30/28/42.These self-assemblies are shown to be bilayers in the liquid ordered phase.They are stable between pH 5 and 9.Over this pH range,the protonation/deprotonation of PA carboxylic group is observed but this change does not appear to alter the stability of these bilayers,a behavior contrasting with that observed for binary mixtures of PA/Chol,and PA/Schol.The multilamellar dispersions formed spontaneously from the PA/Chol/Schol mixture could be successfully extruded to form Large Unilamellar Vesicles (LUVs).These LUVs show interesting permeability properties,linked with their high sterol content.These non-phospholipid liposomes can sustain a pH gradient (pH internal 8/pH external 6) 100 times longer than LUVs made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholesterol,with a molar ratio of 60/40.Moreover,the non-phospholipid LUVs are shown to protect ascorbic acid from an oxidizing environment (1 mM iron(III)).Once entrapped in liposomes,ascorbic acid displays a degradation rate similar to that obtained in the absence of iron(III).These results show the possibility to form novel nanocontainers from a mixture of a monoalkylated amphiphile and sterols,with a good pH stability and showing interesting permeability properties.     

Comparison on effect of hydrophobicity on the antibacterial and antifungal activities of α-helical antimicrobial peptides

HPRP-A1, a 15-mer α-helical cationic peptide, was derived from N-terminus of ribosomal protein L1 (RpL1) of Helicobacter pylori. In this study, HPRP-A1 was used as a framework to obtain a series of peptide analogs with different hydrophobicity by single amino acid substitutions in the center of nonpolar face of the amphipathic helix in order to systematically study the effect of hydrophobicity on biological activities of -helical antimicrobial peptides. Hydrophobicity and net charge of peptides played key roles in the biological activities of these peptide analogs; HPRP-A1 and peptide analogs with relative higher hydrophobicity exerted broad spectrum antimicrobial activity against Gram-negative bacteria, Gram-positive bacteria and pathogenic fungi, but also showed stronger hemolytic activity; the change of hydrophobicity and net charge of peptides had similar effects with close trend and extent on antibacterial activities and antifungal activities. This indicated that there were certain correlations between the antibacterial mode of action and the antifungal mode of action of these peptides in this study. The peptides exhibited antimicrobial specificity for bacteria and fungi, which provided potentials to develop new antimicrobial drugs for clinical practices.     

A new application of multiwavelets: Discrimination of marine algae taxonomic groups with emission-excitation matrix fluorescence

The 3D fluorescence discrimination of phytoplankton classes was investigated by SA4 multiwavelet,GHM multiwavelet,and coifman-2(coif2) wavelet analysis.Belonging to 35 genera of 7 major phytoplankton divisions in the inshore area of China Sea,Single species cultures of 51 phytoplankton species were employed.The second scale vector (Ca2) of SA4,Ca2 of GHM and the third scale vector (Ca3) of coif2 were selected as feature spectra by Bayesian discriminate analysis (BDA).The reference spectra were obtained via hierarchical cluster analysis (HCA).With average high correct discrimination ratios (CDRs),reference spectra were representative to phytoplankton species.For one-algae samples,the average CDRs were 95.6% at genus level and 86.7% at division level.For the laboratory mixed samples,the average CDRs (one division accounted for 25%,75% or 100% of the total biomass) were 86.6%,91.4% and 100% at division level.Moreover,the average CDRs of the dominant species (accounted for 75%) was 79.8% at genus level.Results for the in situ samples were coincided with the microscopic ones at division level with the relative contents of 54.3%-96.5%.The fluorometric discriminating technique was further tested during the cruise in Bohai Sea recently.     

Zinc Porphyrins with a Pyridine‐Ring‐Anchoring Group for Dye‐Sensitized Solar Cells

Anchoring groups are extremely important in controlling the performance of dye‐sensitized solar cells (DSCs). The design and characterization of sensitizers with new anchoring groups, in particular non‐carboxylic acid groups, has become a recent focus of DSC research. Herein, new donor? π? acceptor zinc? porphyrin dyes with a pyridine ring as an anchoring group have been designed and synthesized for applications in DSCs. Photophysical and electrochemical investigations demonstrated that the pyridine ring worked effectively as an anchoring group for the porphyrin sensitizers. DSCs that were based on these new porphyrins showed an overall power‐conversion efficiency of about 4.0 % under full sunlight (AM 1.5G, 100 mW cm^?2).     

Alginate‐Based Microcapsules with a Molecule Recognition Linker and Photosensitizer for the Combined Cancer Treatment

A reactive template method was used to fabricate alginate‐based hydrogel microcapsules. The uniform and well‐dispersed hydrogel capsules have a high drug loading capacity. After they are coated by a folate‐linked lipid mixture on the surface, the capsules possess higher cell uptake efficiency by the molecule recognition between folate and the folate‐receptor overexpressed by the cancer cells. Moreover, in this bioconjugate, the lipid could remarkably reduce the release rate of hydrophilic doxorubicin from the hydrogel microcapsules and encapsulate the hydrophobic photosensitizer hypocrellin B. The biointerfaced capsules could be used as drug carriers for combined treatment against cancer cell proliferation in vitro; this was much more effective than chemotherapy or photodynamic therapy alone.     

Highly selective synthesis of single-walled carbon nanotubes from methane in a coupled Downer-turbulent fluidized-bed reactor

For the synthesis of single-walled carbon nanotubes (SWCNTs) from CH₄ over a Fe/MgO catalyst, we proposed a coupled Downer-turbulent fluidized-bed (TFB) reactor to enhance the selectivity and yield (or production rate) of SWCNTs. By controlling a very short catalyst residence time (1–3 s) in the Downer, only part of Fe oxides can be reduced to form Fe nano particles (NPs) available for the growth of SWCNTs. The percentage of unreduced Fe oxides increased and the yield of SWCNTs decreased accordingly with the increase of catalyst feeding rate in Downer. SWCNTs were preferentially grown on the catalyst surface and inhibited the sintering of the Fe crystallites which would be formed thereafter in the downstream TFB, evidenced by TEM, Raman and TGA. The coupled Downer-turbulent fluidized-bed reactor technology allowed higher selectivity and higher production rate of SWCNTs as compared to TFB alone.     

Preparation of biodegradable and thermoresponsive enzyme–polymer conjugates with controllable bioactivity via RAFT polymerization

The preparation of biodegradable and thermoresponsive enzyme–polymer bioconjugates with controllable enzymatic activity via reversible addition−fragmentation chain transfer (RAFT) polymerization and amidation conjugation reaction is presented. A new 2-mercaptothiazoline ester functionalized RAFT agent with intra-disulfide linkage was synthesized and used as chain transfer agent (CTA) to generate a biocompatible homopolymer, poly(ethyleneglycol) acrylate (polyPEG-A) and a thermoresponsive copolymer of poly(ethyleneglycol) acrylate with di(ethyleneglycol)ethyl ether acrylate [poly(PEG-A-co-DEG-A)]. These biodegradable and thermoresponsive polymers were then conjugated to the surface of glucose oxidase (GOx) under mild condition to afford the biodegradable and thermoresponsive enzyme–polymer conjugates. Cleavage of the polymer chains from the GOx surface obviously recovered the enzymatic activity. The thermoresponsive test of GOx-poly(PEG-A-co-DEG-A) revealed that the bioconjugate exhibited regular enzymatic activity fluctuation upon the temperature change below or above the lower critical solution temperature (LCST). The as-prepared enzyme–polymer conjugates were also characterized using ¹H NMR, UV–vis spectroscopy, polyacrylamide gel electrophoresis (PAGE) and biocatalytic activity tests. These smart enzyme–polymer conjugates would envision promising applications in biotechnology and biomedicine.