Liquid chromatography and electrospray mass spectrometric mapping of peptides from human plasma filtrate

We present a multidimensional approach to map the composition of complex peptide mixtures obtained as crude extract from biological liquids by (1) cation exchange chromatography and (2) subsequent microbore reversed-phase liquid chromatography and electrospray mass spectrometry coupling (LC-MS). Human hemofiltrate is an equivalent to blood and is used to obtain peptide material in large quantities from patients with chronic renal failure. The upper exclusion limit of the filtration membranes used results in a protein-free filtrate containing peptides in a range up to 20 ku. Using this unique peptide source, several thousand peptides were detected and an LC-MS data base of circulating human peptides was created. The search for known peptides by their molecular mass is a reliable method to guide peptide purification.     

Bioorthogonal Cleavage and Exchange of Major Histocompatibility Complex Ligands by Employing Azobenzene‐Containing Peptides

Bioorthogonal cleavable linkers are attractive building blocks for compounds that can be manipulated to study biological and cellular processes. Sodium dithionite sensitive azobenzene‐containing (Abc) peptides were applied for the temporary stabilization of recombinant MHC complexes, which can then be employed to generate libraries of MHC tetramers after exchange with a novel epitope. This technology represents an important tool for high‐throughput studies of disease‐specific T cell responses.     

An overview on chemical derivatization and stability aspects of selected avermectin derivatives

Naturally occurring avermectins (AVMs) and its derivatives are potent endectocide compounds, well-known for their novel mode of action against a broad range of nematode and anthropod animal parasites. In this review, chemical and pharmaceutical aspects of AVM derivatives are described including stability, synthetic and purification processes, impurities and degradation pathways, and subsequent suggestions are made to improve the chemical stability. It has been found out that unique structure of AVM molecules and presence of labile groups facilitated the derivatization of AVM into various compounds showing strong anthelmintic activity. However, the same unique structure is also responsible for labile nature related to sensitive stability profile of molecules. AVMs are found to be unstable in acidic and alkaline conditions. In addition, these compounds are sensitive to strong light, and subsequently presence of photo-isomer in animals treated topically with AVM product is well known. The pharmacoepial recommendations for addition of antioxidant into drug substance, as well as its products, arises from the fact that AVM are very sensitive to oxidation. Formations of solvates, salts, epoxides, reduction of double bonds and developing liquid formulation around pH 6.2, were some chemical approaches used to retard the degradation in AVM. This coherent review will contribute towards the better understanding of the correlation of chemical processes, stability profile and biological activity; therefore, it will help to design the shelf-life stable formulations containing AVMs.     

Identification of a new metabolite of macrolide immunosuppressant, like rapamycin and SDZ RAD, using high performance liquid chromatography and electrospray tandem mass spectrometry

Previously unknown metabolites from the two macrolide immunosuppressants rapamycin (sirolimus) and SDZ RAD [40-O-(2-hydroxyethyl)rapamycin] obtained after in vitro incubation with human liver microsomes have been purified. Structure elucidation was performed by nanoelectrospray ionization tandem mass spectrometry applying low energy collision activated dissociation. This ionization method is, as shown here, a powerful tool to determine metabolic pathways by analysis of even low abundance products. Product ion spectra of the isolated metabolites indicate a new kind of biotransformation reaction for rapamycin and SDZ RAD. The proposed metabolic pathway starts with an ester hydrolysis which leads to a ring-opened structure. A dehydration on C33-C34 and a supplementary hydrogenation at C33-C34 result in a structure similar to the ring-opened isomer with an single bond at C33-C34.     

Global exponential stability of pseudo almost automorphic solutions for delayed Cohen-Grosberg neural networks with measure

Applications of Mathematics - We investigate the Cohen-Grosberg differential equations with mixed delays and time-varying coefficient: Several useful results on the functional space of such...     

Purification and Biochemical Characterization of a Novel Alkaline (Phospho)lipase from a Newly Isolated Fusarium solani Strain

An extracellular lipase from Fusarium solani strain (F. solani lipase (FSL)) was purified to homogeneity by ammonium sulphate precipitation, gel filtration and anion exchange chromatography. The purified enzyme has a molecular mass of 30 kDa as estimated by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The 12 NH₂-terminal amino acid residues showed a high degree of homology with a putative lipase from the fungus Necteria heamatoccocae. It is a serine enzyme, like all known lipases from different origins. Interestingly, FSL has not only lipase activity but also a high phospholipase activity which requires the presence of Ca²⁺ and bile salts. The specific activities of FSL were about 1,610 and 2,414 U/mg on olive oil emulsion and egg-yolk phosphatidylcholine as substrates, respectively, at pH 8.0 and 37 °C. The (phospho)lipase enzyme was stable in the pH range of 5–10 and at temperatures below 45 °C.     

Isolation and characterization of degradation products of moxidectin using LC, LTQ FT-MS, H/D exchange and NMR

This study aimed to evaluate the degradation profile and pathways, and identify unknown impurities of moxidectin under stress conditions. During the experiments, moxidectin samples were stressed using acid, alkali, heat and oxidation, and chromatographic profiles were compared with known impurities given in European Pharmacopeia (EP) monograph. Moxidectin has shown good stability under heat, while reaction with alkali produced 2-epi and ?2,3 isomers (impurities D and E in EP) by characteristic reactions of the oxahydrindene (hexahydrobenzofuran) portion of the macrocyclic lactone. Two new, previously unreported, unknown degradation products, i.e. impurity 1 and impurity 2, detected after acid hydrolysis of moxidectin (impurity 2 was also observed to a lesser extent after oxidation), were isolated from sample matrices and identified using liquid chromatography, NMR, high-resolution FT-ICR MS, and hydrogen/deuterium exchange studies. FTMS analysis showed accurate mass of molecular ion peaks for moxidectin at m/z 640.38412, impurity 1 at m/z 656.37952 and impurity 2 at m/z 611.35684, giving rise to daughter ions traceable up to the seventh levels of MSⁿ experiments and supporting the proposed structures. Both unknown impurities along with moxidectin were fully characterized by ¹H, ¹³C, 1D HMBC and 2D (NOESY, COSY and HSQC) NMR experiments. The interpretation of experimental data positively identified impurity 1 as 3,4-epoxy-moxidectin and impurity 2 as 23-keto-nemadectin. The identification of new impurities and correlation of their chromatographic profiles with the EP method is very useful to establish the stability profile of moxidectin and its preparations, as well as add value to the forthcoming moxidectin finished product European Pharmacopeia monographs.

Clifford Wavelet Entropy for Fetal ECG Extraction

Analysis of the fetal heart rate during pregnancy is essential for monitoring the proper development of the fetus. Current fetal heart monitoring techniques lack the accuracy in fetal heart rate monitoring and features acquisition, resulting in diagnostic medical issues. The challenge lies in the extraction of the fetal ECG from the mother ECG during pregnancy. This approach has the advantage of being a reliable and non-invasive technique. In the present paper, a wavelet/multiwavelet method is proposed to perfectly extract the fetal ECG parameters from the abdominal mother ECG. In a first step, due to the wavelet/mutiwavelet processing, a denoising procedure is applied to separate the noised parts from the denoised ones. The denoised signal is assumed to be a mixture of both the MECG and the FECG. One of the well-known measures of accuracy in information processing is the concept of entropy. In the present work, a wavelet/multiwavelet Shannon-type entropy is constructed and applied to evaluate the order/disorder of the extracted FECG signal. The experimental results apply to a recent class of Clifford wavelets constructed in Arfaoui, et al. J. Math. Imaging Vis. 2020, 62, 73–97, and Arfaoui, et al. Acta Appl. Math. 2020, 170, 1–35. Additionally, classical Haar–Faber–Schauder wavelets are applied for the purpose of comparison. Two main well-known databases have been applied, the DAISY database and the CinC Challenge 2013 database. The achieved accuracy over the test databases resulted in Se = 100%, PPV = 100% for FECG extraction and peak detection.     

Energy and decay width of the πK atom

The energy and the decay width of the πK atom are evaluated in the framework of the quasipotential-constraint theory approach. The main electromagnetic and isospin symmetry breaking corrections to the lowest-order formulas for the energy shift from the Coulomb binding energy and for the decay width are calculated. They are estimated to be of the order of a few per cent. We display formulas to extract the strong interaction S-wave πK scattering lengths from future experimental data concerning the πK atom.PACS 03.65.Pm; 11.10.St; 12.39.Fe; 13.40.Ks