Purification of tryptic peptides for mass spectrometry using polyvinylidene fluoride membrane.

A simple procedure for the purification of tryptic peptides, prior to mass spectrometric analysis, using polyvinylidene fluoride membrane (PVDF) is described. The sensitivity of mass spectrometric analysis is such that minor impurities in tryptic peptide digests suppress the signal obtained. However, we obtained useful signal, from a sample that did not yield any spectra earlier, by purifying the sample using PVDF membrane. For this, the tryptic peptide digest was first spotted on the membrane which was then air-dried and washed. Further, the membrane was extracted with trifluoroacetic acid (TFA) and acetonitrile and subjected to mass spectrometric analysis. This procedure enabled us to identify a cross-reactive D1 antigen on the neutrophil surface that bound antibodies that targeted 60 kD Ro autoantigen in systemic lupus erythematosus, an autoimmune disorder.

Size distribution curves of blood cells in thalassemias and hemoglobin H diseases.

Thalassemias and hemoglobinopathies in Thailand have been examined with a blood cell counter based on electroimpedance principle and obtained size distribution curves of red cells and platelets. Among various disorders, beta-thalassemia/hemoglobin E and homozygous hemoglobin Constant Spring showed severe anemia. Their red cell size distribution curve shifted to the left and overlapped with the platelet size distribution curve. Red cell distribution width expressed by coefficient of variation and the degree of the overlapping were stronger in beta-thalassemia/HbE than HbH. Heterozygous beta-thalassemia showed a narrow red cell distribution curve width with small standard deviation and low England's value. Although the overlapping of size distribution curves cause inaccurate red cell count and platelet count, careful observation of the size distribution curves was proved to have high diagnostic value.