Clustering and Filtering Tandem Mass Spectra Acquired in Data-Independent Mode

Data-independent mass spectrometry activates all ion species isolated within a given mass-to-charge window (m/z) regardless of their abundance. This acquisition strategy overcomes the traditional data-dependent ion selection boosting data reproducibility and sensitivity. However, several tandem mass (MS/MS) spectra of the same precursor ion are acquired during chromatographic elution resulting in large data redundancy. Also, the significant number of chimeric spectra and the absence of accurate precursor ion masses hamper peptide identification. Here, we describe an algorithm to preprocess data-independent MS/MS spectra by filtering out noise peaks and clustering the spectra according to both the chromatographic elution profiles and the spectral similarity. In addition, we developed an approach to estimate the m/z value of precursor ions from clustered MS/MS spectra in order to improve database search performance. Data acquired using a small 3 m/z units precursor mass window and multiple injections to cover a m/z range of 400–1400 was processed with our algorithm. It showed an improvement in the number of both peptide and protein identifications by 8 % while reducing the number of submitted spectra by 18 % and the number of peaks by 55 %. We conclude that our clustering method is a valid approach for data analysis of these data-independent fragmentation spectra. The software including the source code is available for the scientific community.

Electric conductivity of porous glass modified by oxides of bivalent cobalt, nickel, and copper

Multiply repeated operations of porous glass impregnation by aqueous solutions of bivalent cobalt, nickel, and copper nitrates followed by the thermal decomposition of the deposited salts provide a gradual accumulation of oxides in the carrying agent. In all cases, as the surface of glass open channels is filled with oxides, a section of substantial increase in conductance is detected, in which a tentative oxide monolayer is formed. Relations established between conductivity and its activation energy are treated on the basis of the conception of intervalence mechanism of electron transfer in the systems under consideration.     

Non-fragile robust output feedback control of uncertain active suspension systems with stochastic network-induced delay

Nonlinear Dynamics - The vehicle active suspension has attracted considerable attention owing to its great contributions to the vertical dynamics of vehicle. This paper investigates the non-fragile...