Use of short monolithic columns for isolation of low abundance membrane proteins

Convective interaction media (CIM) monoliths provide a stationary phase with a high binding capacity for large molecules and are capable of high flow rates at a very low pressure drop. Used as anion- and cation-exchangers or with affinity ligands such as antibodies, these columns have the potential for processing large volumes of complex biological mixtures within a short time. In the present report, monoclonal antibodies against several rat liver plasma membrane proteins were bound and cross-linked to protein A or protein G CIM affinity columns with a bed volume of only 60 microL. Antigens recognized by bound antibodies and co-eluting (interacting) proteins were rapidly isolated in a single step from either total plasma membrane extracts or subfractions isolated using anion-exchange CIM disk-shaped columns. The isolated antigens and co-eluting proteins were subsequently identified by immunoblot or by LC-MS/MS.     

Phenylselenoetherification of Some Δ5-Alkenols in the Presence of Pyridine, Ag2O, and AgOAc as Additives

Summary. An improved procedure for intramolecular cyclization of some ⁵-alkenols using PhSeX (X=Cl, Br) was developed. We found that cyclization can be facilitated in the presence of pyridine, Ag₂O, and AgOAc as additives. Thus, a catalytic amount of additive influenced higher yields and equimolar amounts achieved almost quantitative yields under extremely mild experimental conditions. The effect of the halide ion of the selenylating reagent was not significant.Received October 21, 2002; accepted (revised) November 13, 2002 Published online August 28, 2003     

N‐(o‐Chloro­phenyl)‐2,5‐di­methyl­pyrrole‐3‐carb­aldehyde

Crystal structure analysis of the title compound, C₁₃H₁₂ClNO, reveals three crystallographically independent mol­ecules in the asymmetric unit. The main conformational difference between these mol­ecules is the orientation of the phenyl rings with respect to the pyrrole rings. The coplanar arrangement of the aldehyde groups attached to the pyrrole rings influences the pyrrole‐ring geometry. The C2—C3 and N1—C5 bonds are noticeably longer than the C4—C5 and N1—C2 bonds. Two independent mol­ecules of the title compound form dimers via intermolecular C—H⃛O hydrogen bonds [D⃛A = 3.400 (3) Å and D—H⃛A = 157°]. The perpendicular orientation of the phenyl and pyrrole rings of one independent mol­ecule and its symmetry‐related mol­ecule allows C—H⃛π interactions, with an H⃛centroid distance of 2.85 Å and a C—H⃛π angle of 155°. The distances between the H atom and the pyrrole‐ring atoms indicate that the C—H bond points towards one of the bonds in the pyrrole ring.     

Synthesis and characterization of some novel cadmium(II) complexes with 3-hydroxypicolinic acid (3-OHpicH): Crystal and molecular structures of [CdI(3-OHpic)(3-OHpicH)(H2O)]2, [Cd(3-OHpic)2(H2O)2] and [Cd(3-OHpic)2]n

Cadmium(II) complexes of 3-hydroxypicolinic acid, namely [CdI(3-OHpic)(3-OHpicH)(H₂O)]₂ (1), [Cd(3-OHpic)₂(H₂O)₂] (2) and [Cd(3-OHpic)₂]_n (3) were prepared and characterized by spectroscopic methods (IR, NMR) and their molecular and crystal structures were determined by X-ray crystal structure analysis. Complexes 1 and 2 were prepared in similar reaction conditions using different cadmium(II) salts: cadmium(II) iodide and cadmium(II) acetate dihydrate, respectively, while 3 was prepared by recrystallization of 2 from N,N-dimethylformamide solution. Various coordination modes of 3-OHpicH in 1–3 were established in the solid state: bidentate N,O-chelated mode in 1 and 2, monodentate mode through the carboxylate O atom from zwitterionic ligand in 1 and bidentate N,O-chelated and bridging mode in 3. In the DMF solution of all prepared complexes, only monodentate mode of 3-OHpicH binding to cadmium(II) through the carboxylate O atom was established by ¹H, ¹³C, ¹⁵N and ¹¹³Cd NMR spectroscopy.     

Continuous separation of Sr, Y and some actinides by mixed solvent anion exchange and determination of 89,90Sr, 238,239Pu and 241Am in soil and vegetation samples

Methodology for the determination of ^89,90Sr, Am and Pu isotopes in complex samples is given. Methodology is based on simultaneous isolation of Sr, Y and actinides from samples by mixed solvent anion exchange chromatography, mutual separation of ^89,90Sr and ⁹⁰Y from actinides, mutual separation of Th, Pu and Am by extraction chromatography, quantitative determination of ^89,90Sr by Cherenkov counting and quantitative determination of Pu and Am isotopes in soil and vegetation samples by alpha spectrometry. It is shown that Y and Sr can be efficiently separated from alkaline, alkaline earth and transition elements as well as from lanthanides and actinides on the column filed by strong base anion exchanger in nitrate form and 0.25?M HNO₃ in mixture of ethanol and methanol as eluent. It is also shown that Pu, Am and Th strongly binds on the mentioned column, can be separated from number of elements and easily be eluted from column by water. After elution actinides were mutually separated on TRU column and electrodeposited on stainless steel disc. Examination of conditions of electrodeposition was shown that chloride-oxalate electrolyte with addition of DTPA in presence of sodium hydrogen sulphate in cell with cooling and rotating platinum anode enables deposition of actinides within 1?h by 0.8?A?cm^?2 current density. Obtained peaks FWHM for Pu, Am and Th isotopes are between 27 and 40?keV. Scanning electron microscopy picture and ED XRF analysis of electroplated discs showed that actinide deposition is followed by iron oxide formation on disc surface. The methodology was tested by determination of ^89,90Sr, Am and Pu isotopes in ERA proficiency testing samples (low level activity samples). Obtained results shows that ^89,90Sr, ²⁴¹Am and ^238,239Pu can be simultaneously separated on anion exchange column, ^89,90Sr can be determined by Cherenkov counting with a satisfactory accuracy and limit of determination within 1?C3?days after separation. ²⁴¹Am and ^238,239Pu can easily be separated on TRU column and determined after electrodeposition with acceptable accuracy within 1?day.     

Chiral Hexa‐ and Nonamethylene‐Bridged Bis(L‐Leu‐oxalamide) Gelators: The First Oxalamide Gels Containing Aggregates with a Chiral Morphology

Chiral amino acid‐ and amino alcohol‐oxalamides are well‐known as versatile and efficient gelators of various lipophilic and polar organic solvents and water. To further explore the capacity of the amino acid/oxalamide structural fragment as a gelation‐generating motif, the dioxalamide dimethyl esters 1₆Me and 1₉Me , and dicarboxylic acid 2₆OH / 2₉OH derivatives containing flexible methylene bridges with odd ( 9 ; n=7) and even ( 6 ; n=4) numbers of methylene groups were prepared. Their self‐assembly motifs and gelation properties were studied by using a number of methods (FTIR, ¹H NMR spectroscopy, CD, TEM, DSC, XRPD, molecular modeling, MMFF94, and DFT). In contrast to the previously studied chiral bis(amino acid or amino alcohol) oxalamide gelators, in which no chiral morphology was ever observed in the gels, the conformationally more flexible 1₆Me , 1₉Me , 2₆OH , and 2₉OH provide gelators that are capable of forming diverse aggregates of achiral and chiral morphologies, such as helical fibers, twisted tapes, nanotubules, straight fibers, and tapes, in some cases coexisting in the same gel sample. It is shown that the differential scanning calorimetry (DSC)‐determined gelation enthalpies could not be correlated with gelator and solvent clogP values. Spectroscopic results show that intermolecular hydrogen‐bonding between the oxalamide units provides the major and self‐assembly directing intermolecular interaction in the aggregates. Molecular modeling studies reveal that molecular flexibility of gelators due to the presence of the polymethylene bridges gives three conformations ( zz , p1 , and p2 ) close in energy, which could form oxalamide hydrogen‐bonded layers. The aggregates of the p1 and p2 conformations tend to twist due to steric repulsion between neighboring iBu groups at chiral centers. The X‐ray powder diffraction (XRPD) results of 1₆Me and 1₉Me xerogels prove the formation of p1 and p2 gel aggregates, respectively. The latter results explain the formation of gel aggregates with chiral morphology and also the simultaneous presence of aggregates of diverse morphology in the same gel system.     

Effect of Functionalized Benzene Derivatives as Potential Hole Scavengers for BiVO4 and rGO-BiVO4 Photoelectrocatalytic Hydrogen Evolution

Sustainable hydrogen production is one of the main challenges today in the transition to a green and sustainable economy. Photocatalytic hydrogen production is one of the most promising technologies, amongst which BiVO₄-based processes are highly attractive due to their suitable band gap for solar-driven processes. However, the performance of BiVO₄ alone in this role is often unsatisfactory. Herein we report the improvement of BiVO₄ performance with reduced graphene oxide (rGO) as a co-catalyst for the photoelectrochemical water splitting (PEC-WS) in the presence of simple functionalized benzene derivatives (SFBDs), i.e., phenol (PH), benzoic acid (BA), salicylic acid (SA), and 5-aminosalicylic acid (5-ASA) as potential photogenerated hole scavengers from contaminated wastewaters. Linear sweep voltammetry and chronoamperometry, along with electrochemical impedance spectroscopy were utilized to elucidate PEC-WS performance under illumination. rGO has remarkably improved the performance of BiVO₄ in this role by decreasing photogenerated charge recombination. In addition, 5-ASA greatly improved current densities. After 120 min under LED illumination, 0.53 μmol of H₂ was produced. The type and concentration of SFBDs can have significant and at times opposite effects on the PEC-WS performance of both BiVO₄ and rGO-BiVO₄.