Category Bio Analysis Matrix Method UHPLC

A rapid, sensitive and specific high-performance liquid chromatographic (HPLC) method for the separation and quantification of L-methionine in plasma has been developed. After derivatization of plasma amino acids with o-phthalaldehyde (OPA), a 50 microl sample was loaded on a reversed-phase Supelcosil LC-18-DB column (particle size 5 microm, 25 cm x 4.6 mm, 120A pores). A customized gradient pr...

Quantitation of amino acids in complex matrixes without derivatization is advantageous; however, difficulties exist in both the separation and the detection of those compounds. A validated method that is based on the use of volatile ion-pair liquid chromatography coupled to stable isotope dilution tandem mass spectrometry has been developed for the simple and accurate quantitation of underivati...

We investigated the role of gonococcal outer membrane protein PII (also called Opa protein) in nonopsonic adherence to human neutrophils. Gonococcal outer membranes, purified Opa in detergent (Opa), purified Opa in liposomes (Opa+ lips), and peptides composing the second hypervariable (HV2) region of OpaB (strain FA1090) in liposomes (pepHV2 lips) were tested for their abilities to inhibit subs...

T cells may interact with a number of bacterial surface antigens, an encounter which has the potential to downmodulate host immune responses. Neisseria meningitidis, a human colonizer and an agent of septicemia and meningitis, expresses Opa proteins which interact with the CEACAM1 receptor expressed on activated T cells. Since CEACAM1 can act as an inhibitory receptor and T cells in subepitheli...

The opacity (Opa) proteins of Neisseria gonorrhoeae are a family of outer membrane proteins demonstrating phase and antigenic variation. N. gonorrhoeae strain FA0190 has 11 opa loci that encode at least 8 antigenically distinct Opa proteins. To determine if expression of one Opa protein or a subset of them is favored during gonococcal infection, we inoculated Opa-negative variants of strain FA1...

Neisseria meningitidis is a major global pathogen causing invasive disease with a mortality of 5-10%. Most disease in developed countries is caused by serogroup B infection, against which there is no universal vaccine. Opacity-associated adhesin (Opa) proteins are major meningococcal outer membrane proteins, which have shown recent promise as a potential novel vaccine. Immunisation of mice with...

To understand the rates and mechanisms of Neisseria gonorrhoeae opa gene variation, the 11 opa genes were amplified independently so that an opa allelic profile could be defined for any isolate from the sequences at each locus. The opa allelic profiles from 14 unrelated isolates were all different, with no opa alleles shared between isolates. Examination of very closely related isolates from se...

OBJECTIVES To use a molecular typing method (opa-typing) to characterise gonococcal isolates obtained from men who have sex with men (MSM) attending a genitourinary medicine (GUM) clinic in Edinburgh during 2001. To compare the results of opa-typing with A/S (auxotype/serovar) phenotyping, and with epidemiological information obtained by contact tracing. METHODS Isolates were opa-typed by a P...