Solid-phase extraction of phospholipids from hemoglobin solutions using Empore styrene–divinylbenzene disks

Styrene–divinylbenzene Empore disks were investigated for the extraction of phospholipids from red blood cells or aqueous solutions of hemoglobin as a means to reduce the time and solvent use required in sample preparation. Red blood cells are the source for hemoglobin used in the preparation of a hemoglobin-based oxygen carrier which is being developed to replace blood in transfusion therapy. Phospholipids are a major component of the membrane of red blood cells, and are toxic when administered directly into the vasculature. Sensitive analytical methods are required to detect phospholipids to ensure that concentrations in purified hemoglobin are well below toxic levels. This requires isolation from large volumes of purified hemoglobin solutions. The method described utilizes Empore disks to extract phospholipids from 30 ml of stroma free Hb preparations. Phosphatidylethanolamine, phosphatidylinositol, phosphatidylcholine and sphingomyelin were recovered with an average of 92% yield. The recovery of phosphatidylserine was 65%. The use of solvent and time required for sample preparation were reduced by an average of 80% relative to liquid–liquid extraction. The capacity of the 47-mm disk for the total of five phospholipids exceeds 0.3 mg. The method has been used for quantitation of phospholipids in red blood cells and stroma free hemoglobin solutions.     

A lactational study of the composition and integrity of casein micelles from the milk of the tammar wallaby (Macropus eugenii)

The amount of casein found in the milk of the tammar wallaby increases as lactation progresses. The increase is due to increasing amounts of β-casein; the α-casein remains largely constant. The α-casein is the more highly phosphorylated; the most abundant form is the 10-P, throughout lactation. The level of phosphorylation of β-casein shifts to lower average values in late lactation, possibly indicating the enzymatic reaction is overloaded by the increasing amounts of β-casein. Unlike bovine casein micelles, the wallaby micelles are not completely disrupted at pH 7.0 by sequestration of their calcium content with ethylene diamine tetraacetic acid (EDTA). Complete disruption only follows the addition of sodium dodecyl sulphate, indicating considerably greater importance for hydrophobic bonds in maintaining their integrity. This micellar behaviour indicates that, despite the evolutionary divergence of marsupials millennia ago, the caseins of wallaby milk assemble into micelles in much the same fashion as in bovine milk.     

Multiplex SNP discrimination

Multiplex hybridization reactions of perfectly matched duplexes and duplexes containing a single basepair mismatch (SNPs) were investigated on DNA microarrays. Effects of duplex length, G-C percentage, and relative position of the SNP on duplex hybridization and SNP resolution were determined. Our theoretical model of multiplex hybridization accurately predicts observed results and implicates target concentration as a critical variable in multiplex SNP detection.     

An essential saccharide binding domain for the mAb 2C7 established for Neisseria gonorrhoeae LOS by ES-MS and MSn

A study of bacterial surface oligosaccharides were investigated among different strains of Neisseria gonorrhoeae to correlate structural features essential for binding to the MAb 2C7. This epitope is widely expressed and conserved in gonococcal isolates, characteristics essential to an effective candidate vaccine antigen. Sample lipooligosaccharides (LOS), was prepared by a modification of the hot phenol-water method from which de-O-acetylated LOS and oligosaccharide (OS) components were analyzed by ES-MS-CID-MS and ES-MSnin a triple quadrupole and an ion trap mass spectrometer, respectively. Previously documented natural heterogeneity was apparent from both LOS and OS preparations which was admixed with fragments induced by hydrazine and mild acid treatment. Natural heterogeneity was limited to phosphorylation and antenni extensions to the alpha-chain. Mild acid hydrolysis to release OS also hydrolyzed the beta(1-->6) glycosidic linkage of lipid A. OS structures were determined by collisional and resonance excitation combined with MS and multistep MSn which provided sequence information from both neutral loss, and nonreducing terminal fragments. A comparison of OS structures, with earlier knowledge of MAb binding, enzyme treatment, and partial acid hydrolysis indicates a generic overlapping domain for 2C7 binding. Reoccurring structural features include a Hepalpha(1-->3)Hepbeta(1-->5)KDO trisaccharide core branched on the nonreducing terminus (Hep-2) with an alpha(1-->2) linked GlcNAc (gamma-chain), and an alpha-linked lactose (beta-chain) residue. From the central heptose (Hep-1), a beta(1-->4) linked lactose (alpha-chain), moiety is required although extensions to this residue appear unnecessary.      

Application of electrospray ionization mass spectrometry for studying human immunodeficiency virus protein complexes

Mass spectrometry (MS) with electrospray ionization (ESI) has shown utility for studying noncovalent protein complexes, as it offers advantages in sensitivity, speed, and mass accuracy. The stoichiometry of the binding partners can be easily deduced from the molecular weight measurement. In many examples of protein complexes, the gas phase-based measurement is consistent with the expected solution phase binding characteristics. This quality suggests the utility of ESI-MS for investigating solution phase molecular interactions. Complexes composed of proteins from the human immunodeficiency virus (HIV) have been studied using ESI-MS. Multiply charged protein dimers from HIV integrase catalytic core (F185K) and HIV protease have been observed. Furthermore, the ternary complex between HIV protease dimer and inhibitor pepstatin A was studied as a function of solution pH. Zinc binding to zinc finger-containing nucleocapsid protein (NCp7) and the NCp7-psi RNA 1:1 stoichiometry complex was also studied by ESI-MS. No protein-RNA complex was observed in the absence of zinc, consistent with the role of the zinc finger motifs for RNA binding. Proteins Suppl. 2:28–37, 1998. © 1998 Wiley-Liss, Inc.     

1,25-dihydroxyvitamin D3 selectively induces increased expression of the Na,K-ATPase β1 subunit in avian myelomonocytic cells without a concomitant change in Na,K-ATPase activity

Treatment of avian myelomonocytic cells with 1,25-dihydroxyvitamin D₃ (1,25(OH)2D3) results in an approximately two fold increase in levels of Na,K-ATPase β1 subunit mRNA and protein (both total and plasma membrane-associated). The changes in β1 subunit expression occur in the absence of a detectable increase in expression of any of the three α subunit isoforms or in Na,K-ATPase activity. The selective induction of the expression of the β subunit in avian myelomonocytic cells by 1,25(OH)2D3 reveals a previously unobserved feature of the regulation of Na,K-ATPase expression, while the targeting of β subunit polypeptides to the plasma membrane in the absence of a corresponding increase in active Na,K-ATPase suggests that, in these cells, transport of the β subunit to the plasma membrane may be independent of its binding to the α subunit. J. Cell. Physiol. 172:221–229, 1997. © 1997 Wiley-Liss, Inc.     

Negative emotional biases in late chronotypes

Increasing evidence suggests evening chronotypes are at increased risk for developing depression. Here, we examined if, similar to acutely depressed patients, evening chronotype individuals display biases in emotional face recognition. Two hundred and twenty-six individuals completed an online survey including measures of sleep quality, depression/anxiety and chronotype followed by a simple emotion recognition task presenting male and female faces morphed in 10 steps between 0 (neutral) and 100% sad or happy. Evening chronotype was associated with increased recognition of sad facial expressions independently of sleep quality, mood, age and gender. The current results extend previous work indicating that negative biases in emotional processing are present in evening chronotypes and may have important implications for the prevention and treatment of depression in these vulnerable individuals.