Using HPTLC/DESI-MS for peptide identification in 1D separations of tryptic protein digests

Desorption electrospray ionization mass spectrometry (DESI-MS) was investigated as a method to detect and identify peptides from tryptic digests of cytochrome c and myoglobin separated on ProteoChrom HPTLC Silica gel 60 F(254s) plates and ProteoChrom HPTLC Cellulose sheets. Full-scan mass spectra and data-dependent tandem mass spectra were acquired in separate plate scans and used to identify peptide ions. Peptide distributions along the development lane were mapped for each separated protein digest. Signal levels ranged over several orders of magnitude. In general, highest signal levels were obtained for the peptides with the highest R (f) values on a plate, while peptides with very low R (f) values were often not detected. Sequence coverages for cytochrome c were 58% for the digest separated on the silica gel plate and 72% for the separation on the cellulose sheet; myoglobin sequence coverages were 62% and 68% on silica gel and cellulose, respectively. Weak correlations between peptide hydrophilicity and R (f) values on the silica gel and cellulose plates were found, with the more hydrophilic peptides having lower R (f) values.     

Freezing and Melting of Water Confined in Silica Nanopores

In nanosized pores, liquid water can be thermodynamically stable down to temperatures well below the limit of homogeneous nucleation of bulk water (～235 K). Studies of water in such pores therefore offer an opportunity to reveal the anomalous behavior of deeply supercooled water. Herein we focus on recent studies of the limits of freezing and melting of water in the cylindrical pores of ordered mesoporous silicas with pore diameters in the range of 2–10 nm, based on vapor sorption measurements, calorimetric studies, NMR spectroscopy and cryoporometry, and neutron diffraction studies.     

Chemosensor for the optical detection of aliphatic amines and diamines

Two new chemosensor dyes with either one or two trifluoroacetophenone recognition moieties have been investigated in terms of reversibly interacting with amines and diamines.     

Development of a validated liquid chromatography/tandem mass spectrometry method for the distinction of thyronine and thyronamine constitutional isomers and for the identification of new deiodinase substrates

Thyronines (THs) and thyronamines (TAMs) are two groups of endogenous iodine-containing signaling molecules whose representatives differ from each other only regarding the number and/or the position of the iodine atoms. Both groups of compounds are substrates of three deiodinase isozymes, which catalyze the sequential reductive removal of iodine from the respective precursor molecule. In this study, a novel analytical method applying liquid chromatography/tandem mass spectrometry (LC-MS/MS) was developed. This method permitted the unequivocal, simultaneous identification and quantification of all THs and TAMs in the same biological sample. Furthermore, a liquid-liquid extraction procedure permitting the concurrent isolation of all THs and TAMs from biological matrices, namely deiodinase (Dio) reaction mixtures, was established. Method validation experiments with extracted TH and TAM analytes demonstrated that the method was selective, devoid of matrix effects, sensitive, linear over a wide range of analyte concentrations and robust in terms of reproducible recoveries, process efficiencies as well as intra-assay and inter-assay stability parameters. The method was applied to study the deiodination reactions of iodinated THs catalyzed by the three deiodinase isozymes. With the HPLC protocol developed herein, sufficient chromatographic separation of all constitutional TH and TAM isomers was achieved. Accordingly, the position of each iodine atom removed from a TH substrate in a Dio-catalyzed reaction was backtracked unequivocally. While several established deiodination reactions were verified, two as yet unknown reactions, namely the phenolic ring deiodination of 3',5'-diiodothyronine (3',5'-T2) by Dio2 and the tyrosyl ring deiodination of 3-monoiodothyronine (3-T1) by Dio3, were newly identified.