[Probabilistic calculations of biomolecule charge states that generate mass spectra of multiply charged ions].

In this work, information relating to charge states of biomolecule ions in solution obtained using the electrospray ionization mass spectrometry of different biopolymers is analyzed. The data analyses have mainly been carried out by solving an inverse problem of calculating the probabilities of retention of protons and other charge carriers by ionogenic groups of biomolecules with known primary structures. The approach is a new one and has no known to us analogues. A program titled "Decomposition" was developed and used to analyze the charge distribution of ions of native and denatured cytochrome c mass spectra. The possibility of splitting of the charge-state distribution of albumin into normal components, which likely corresponds to various conformational states of the biomolecule, has been demonstrated. The applicability criterion for using previously described method of decomposition of multidimensional charge-state distributions with two charge carriers, e.g., a proton and a sodium ion, to characterize the spatial structure of biopolymers in solution has been formulated. In contrast to known mass-spectrometric approaches, this method does not require the use of enzymatic hydrolysis or collision-induced dissociation of the biopolymers.

A new approach to data reduction and evaluation in high-resolution time-of-flight mass spectrometry using a time-to-digital convertor data-recording system.

A new effective and robust approach to the detection of incompletely resolved peaks, and evaluation of their parameters in high-resolution time-of-flight mass spectra for time-to-digital convertor (TDC) data acquisition mode, is described. The method is based on fast construction of a smoothed continuous curve that approximates the initial data (transformed to a constant relative width of time intervals for ion counting) with respect to precision of measurements. The first derivative of this curve is used for correction of skewness of the peak shape as far as possible. A contribution of the second derivative is subtracted from the smoothed curve for better resolution of partially resolved peaks. The comparison of local maxima of this resulting final curve with those for the initial smoothed curve allows reliable detection of the peaks and to test whether or not they are spoiled by overlapping. Ion counting performed by TDC gives an opportunity to estimate standard deviations of peak locations and their intensities. These values proved to be close to theoretically minimal standard deviations for these parameters for single fully resolved peaks. Thus, estimates of the main parameters of mass peaks by the described method are close to statistically efficient estimators for these parameters.

Electrospray mass spectrometric study of melittin trypsinolysis by a kinetic approach.

The kinetics of tryptic digestion of melittin was studied by combined electrospray ionization time-of-flight mass spectrometry and high-performance liquid chromatography. The ratios of the kinetic constants for cleavage of the peptide bonds that are susceptible to trypsin action were determined. It is shown that trypsin does not manifest affinity for the hydrolysis of the peptide bonds inside the Arg,Lys cluster series as efficiently as it cleaves the peptide at the separately localized Lys residue. This feature demonstrates clearly the advantage of the kinetic approach to tryptic mapping of proteins. The kinetic approach allows the determination of not only discrete structural segments in protein structure but also their relative locations and their amino acid sequences. Using the melittin digests and some artificially prepared amino acids and dipeptides mixtures as models, it is shown that the presence and nature of basic amino acids predetermines the charge states of the molecules analyzed by electrospray but not the yields of their ions. The aliphatic parts of the molecules seem to be more important in determining the actual ion yields.