Gas Phase Ion Chemistry to Determine Isoaspartate in a Peptide Backbone.

Proof of concept evidence is presented for a new method for the determination of isoaspartate, an important post-translational modification. Chemical derivatization is performed using common reagents for the modification of carboxylic acids and shown to yield suitable diagnostic information with regard to isomerization at the aspartate residue. The diagnostic gas phase chemistry is probed by collision-induced dissociation mass spectrometry, on the timescale of the MS experiment and semi-quantitative calibration of the percentage of isoaspartate in a peptide sample is demonstrated. Graphical Abstract ᅟ.

Characteristics of HIV-infected pregnant women in the Bahamas.

The Commonwealth of the Bahamas has one of the highest rates of acquired immunodeficiency syndrome (AIDS) in the English-speaking Caribbean. A seroprevalence study of pregnant women attending antenatal clinics in New Providence in 1990-91 showed that of 3,914 pregnant women tested, 2.9% were human immunodeficiency virus (HIV) infected. Women born in the Bahamas constituted 79.2% of the women tested; 17.7% were born in Haiti. The rate of HIV infection was 2.5% in the Bahamian women as compared with 4.5% in those born in Haiti. The highest incidence was in women aged 25-34 years and in women who had multiple pregnancies. There was a significant association with a history of crack cocaine use by the Bahamian women. There was also a significant association between a lack of education and HIV infection in this group. There was a lower rate of condom use among women with less education and also among women in common-law relationships, but the association of lack of condom use and HIV infection did not reach statistical significance.

Presence of the seven transmembrane thrombin receptor on human tumour cells: effect of activation on tumour adhesion to platelets and tumor tyrosine phosphorylation.

Thrombin-treated tumour cells enhance their adhesion to platelets, fibronectin and von Willebrand factor in vitro, and enhanced their pulmonary metastasis in mice in vivo. A unique seven transmembrane spanning thrombin receptor has recently been cloned which is activated following thrombin proteolysis of the N-terminal end of the receptor with exposure of a tethered ligand. An N-terminal 14-mer (SFLLRNPNKYEPF) or 6-mer (SFLLRN) of the tethered ligand can serve as a thrombin receptor activation peptide (TRAP) by mimicking the action of thrombin on platelets, endothelial cells and smooth muscle cells. We have examined six human tumour cell lines for their response to TRAP, for the presence of this thrombin receptor mRNA by RT-PCR, protein by immunoblot and for their in vitro and in vivo response to TRAP. All six cell lines contain the receptor mRNA, and when treated with 100 microM 6-mer TRAP or 1 u/ml thrombin increase their adhesion to platelets 2-3-fold. Four of the six cell lines undergo tyrosine phosphorylation within 30 s to 1 min after exposure to 6-mer TRAP or thrombin. Thus tumour cells respond to thrombin via activation of their seven transmembrane spanning thrombin receptor.