We have studied the double ionization of helium and other rare gases using an electron-ion coincidence technique. With this scheme, the electron energy spectrum correlated to the creation of a doubly charged ion may be compiled. In all cases, the observed double ionization electron distributions are similar and enhanced at high energies, while the single ionization spectra exhibit distinct diff...

BACKGROUND Germ-line mutations of the breast cancer susceptibility gene-1 (BRCA1) increase the susceptibility to tumorigenesis. The function of BRCA1 is to regulate critical cellular processes, including cell cycle progression, genomic integrity, and apoptosis. Studies on the regulation of BRCA1 have focused intensely on transcription and phosphorylation mechanisms. Proteolytic regulation of BR...

BACKGROUND Matrix effects can profoundly reduce the performance of electrospray ionization mass spectrometry. Preliminary observations indicated that the methanol used in the mobile phase could be a source of differential ionization or ion suppression. METHODS Drug stability studies, analysis of biological extracts, mixing experiments, and postcolumn infusions were used to test 9 commercial m...

The mass spectrometric analysis of protein phosphorylation is still far from being routine, and the outcomes thereof are often unsatisfying. Apart from the inherent problem of substoichiometric phosphorylation, three arguments as to why phosphorylation analysis is so problematic are often quoted, including (a) increased hydrophilicity of the phosphopeptide with a concomitant loss during the loa...

Chemical hardness (), absolute electronegativity (), and electrophilicity () have importantapplications in inorganic chemistry. These concepts are defined quantitatively as � � �� � ����,� � �� � ����, � � ������Where I is the ionization energy and A is the electron affinity. In thisstudy, graphical method was used to see the relation of electron configuration with chemicalhardness, absolute el...