Vitamin A aldehyde-taurine adducts function in photoreceptor cells.

To facilitate the movement of retinoids through the visual cycle and to limit nonspecific chemical reaction, multiple mechanisms are utilized to handle these molecules when not contained within the binding pocket of opsin. Vitamin A aldehyde is sequestered by reversible Schiff base formation with phosphatidylethanolamine (PE) and subsequently undergoes NADPH-dependent reduction. Otherwise inefficient handling of retinaldehyde can lead to the formation of fluorescent di-retinal compounds within the outer segments of photoreceptor cells. These bisretinoid fluorophores initiate photooxidative processes having adverse consequences for retina. Various carrier proteins confer water solubility and maintain the 11-cis-retinoid configuration. Mechanisms for sequestration of retinoid include the formation of a reversible Schiff base between retinaldehyde and taurine (A1-taurine, A1T), the most abundant amino acid in photoreceptor cells. Here we have undertaken to examine the effects of taurine depletion using the transport inhibitors guanidinoethyl sulfonate (GES) and ß-alanine. Oral treatment of BALB/cJ mice with ß-alanine reduced ocular A1T and the mice exhibited significantly lower scotopic and photopic a-wave amplitudes. As a secondary effect of retinal degeneration, A1T was not detected and taurine was significantly reduced in mice carrying a P23H opsin mutation. The thinning of ONL that is indicative of reduced photoreceptor cell viability in albino Abca4-/- mice was more pronounced in ß-alanine treated mice. Treatment of agouti and albino Abca4-/- mice with ß-alanine and GES was associated with reduced bisretinoid measured chromatographically. Consistent with a reduction in carbonyl scavenging activity by taurine, methylglyoxal-adducts were also increased in the presence of ß-alanine. Taken together these findings support the postulate that A1T serves as a reservoir of vitamin A aldehyde, with diminished A1T explaining reduced photoreceptor light-sensitivity, accentuated ONL thinning in Abca4-/- mice and attenuated bisretinoid formation.

A simple "turn-on" fluorescence sensor for salicylaldehyde skeleton based on switch of PET-AIE effect.

The selective detection of salicylaldehyde skeleton is of great significance in phytochemistry and biological research but rarely reported. In this research, a simple and highly selective "turn-on" fluorescence sensor (CDB-Am) for salicylaldehyde skeleton was developed based on switch of photoinduced electron transfer (PET) and aggregation-induced emission (AIE). CDB-Am bearing amino-cyanodistyrene structure responded to salicylaldehyde in the range of 3.1 to 40 µM with a detection limit of 0.94 µM. The sensing process of formation of Schiff-base adduct CDB-SA was confirmed by 1H NMR, MS, and FT-IR spectra, revealing that a recovered AIE property accounted for the turn-on fluorescence response of CDB-Am and the intramolecular hydrogen bonding played a crucial role in the disruption of PET process. This sensing ability was successfully applied for both fluorescence qualitative test of salicylaldehyde skeleton on TLC analysis and quantitative detection of salicylaldehyde skeleton with good accuracy in the root bark of Periploca sepium, suggesting the extensive applications in phytochemistry and traditional Chinese herbal medicine. Furthermore, CDB-Am exhibited the first excellent fluorescence imaging ability in detecting salicylaldehyde skeleton in a living system. This work supplied a new strategy of preparing a novel "turn-on" fluorescence probe for detecting salicylaldehyde skeleton in complex environments and living bodies.

Mechanochemical generation of Schiff bases and Amadori products and utilization of diagnostic MS/MS fragmentation patterns in negative ionization mode for their analysis.

The use of tandem mass spectrometry under positive ionization mode was previously developed as a tool for distinguishing isomeric Schiff bases and Amadori products. In this paper, similar diagnostic MS/MS fragmentation patterns were identified under negative ionization mode and was utilized to study the composition of mechanochemically generated Maillard reaction mixtures. The major diagnostic ion of the Schiff base was found to be a diose attached to the amino acid residue, while that of the Amadori compound was a triose. The structures of the diagnostic ions were confirmed through isotope labeling technique and elemental composition. Furthermore, application of this technique showed that ball milling of glucose with different amino acids almost exclusively results in the formation of a mixture of Schiff bases and Amadori compounds, and that amino acids with basic side chains generated more Schiff bases and those with acidic side chains generated more Amadori products.

Quantitative Profiling of Protein-Derived Electrophilic Cofactors in Bacterial Cells with a Hydrazine-Derived Probe.

Post-translational modification of proteins can form electrophilic cofactors that serve as a catalytic center. The derived electrophilic cofactors greatly expand protein activities and functions. However, there are few studies concerning how to profile the electrophiles in bacteria. Herein, we utilized a clickable probe called propargyl hydrazine to profile the protein-derived electrophilic cofactors in Escherichia coli (E. coli) cells. Since the cofactors are mostly carbonyl groups, the hydrazine-based probe can specifically react with the cofactors to form a Schiff base. The labeled proteins were then pulled down for mass spectrometry (MS) analysis. Fourteen proteins were shown to undergo enrichment by the probe and competitive binding by its analogue, propyl hydrazine. The identified proteins were further analyzed with targeted proteomics based on parallel reaction monitoring (PRM). Using this strategy, we obtained a global portrait of protein electrophiles in bacterial cells, among which the proteins of speD and panD were previously reported to derive pyruvoyl group as an electrophilic center while lpp can retain N-terminal formyl methionine. This quantitative chemical proteomics strategy can be used to find out protein electrophiles in bacteria and holds great potential to further characterize the protein functions.

Chemoproteomics Reveals Chemical Diversity and Dynamics of 4-Oxo-2-nonenal Modifications in Cells.

4-Oxo-2-nonenal (ONE) derived from lipid peroxidation modifies nucleophiles and transduces redox signaling by its reactions with proteins. However, the molecular interactions between ONE and complex proteomes and their dynamics in situ remain largely unknown. Here we describe a quantitative chemoproteomic analysis of protein adduction by ONE in cells, in which the cellular target profile of ONE is mimicked by its alkynyl surrogate. The analyses reveal four types of ONE-derived modifications in cells, including ketoamide and Schiff-base adducts to lysine, Michael adducts to cysteine, and a novel pyrrole adduct to cysteine. ONE-derived adducts co-localize and exhibit crosstalk with many histone marks and redox sensitive sites. All four types of modifications derived from ONE can be reversed site-specifically in cells. Taken together, our study provides much-needed mechanistic insights into the cellular signaling and potential toxicities associated with this important lipid derived electrophile.

Expanding the potential of chiral chromatography for high-throughput screening of large compound libraries by means of sub-2µm Whelk-O 1 stationary phase in supercritical fluid conditions.

With the aim of exploring the potential of ultra-fast chiral chromatography for high-throughput analysis, the new sub-2 micron Whelk-O 1 chiral stationary phase (CSP) has been employed in supercritical fluid conditions to screen 129 racemates, mainly of pharmaceutical interest. By using a 5-cm long column (0.46cm internal diameter), a single co-solvent (MeOH) and a 7-min gradient elution, 85% of acidic and neutral analytes considered in this work have been successfully resolved, with resolution (Rs) larger than 2 in more than 65% of cases. Moreover, almost a half of basic samples that, for their own characteristics, are known to be difficult to separate on Whelk-O 1 CSP, have shown Rs greater than 0.3. The screening of the entire library could be accomplished in less than 24h (single run) with 63% of positive score. For well-resolved enantiomers (Rs roughly included between 1 and 3), we show that method transfer from gradient to isocratic conditions is straightforward. In many cases, isocratic ultra-fast separations (with analysis time smaller than 60s) have been achieved by simply employing, as isocratic mobile phase, the eluent composition at which the second enantiomer was eluted in gradient mode. By considering the extension and variety of the library in terms of chemico-physical and structural properties of compounds and numerousness, we believe that this work demonstrates the real potential of the technique for high-throughput enantioselective screening.

Investigation of the reactions of acrylamide during in vitro multistep enzymatic digestion of thermally processed foods.

This study investigated the fate of acrylamide in thermally processed foods after ingestion. An in vitro multistep enzymatic digestion system simulating gastric, duodenal and colon phases was used to understand the fate of acrylamide in bakery and fried potato products. Acrylamide levels gradually decreased through gastric, duodenal and colon phases during in vitro digestion of biscuits. At the end of digestion, acrylamide reduction was between 49.2% and 73.4% in biscuits. Binary model systems composed of acrylamide and amino acids were used to understand the mechanism of acrylamide reduction. High-resolution mass spectrometry analyses confirmed Michael addition of amino acids to acrylamide during digestion. In contrast to bakery products, acrylamide levels increased significantly during gastric digestion of fried potatoes. The Schiff base formed between reducing sugars and asparagine disappeared rapidly, whereas the acrylamide level increased during the gastric phase. This suggests that intermediates like the Schiff base that accumulate in potatoes during frying are potential precursors of acrylamide under gastric conditions.

[New in conservative therapy of chronic sialoadenitis].

The use of vasaprostan nucellary form in complex treatment of patients with chronic parenchymatous sialoadenitis in a stage of an aggravation in the field of amazed salivary gland renders good therapeutic effect, which is proved by clinical data and results of reografic and bioсemical researches (laktoferrin concentration, middlemolecularpeptids and sum of primary and secondary products of hyperoxide acidification lipids, basis of Shiff).

Characterization of a meso-chiral isomer of a hexanuclear Cu(II) cage from racemization of the L-alanine Schiff base.

We are reporting structural characterization of two new hexanuclear cages (H3O)2[Cu3(µ3-OH)(µ3-NH3)(0.5)(L)3]2·8H2O (1) and (H3O)2[Cu3(µ3-OH)(µ3-H2O)(0.5)(L)3]2·8H2O (1a) where L(2-) is the dianionic form of the Schiff base of L-alanine and salicylaldehyde. The complex 1 has two C3 symmetric hydroxo bridged trinuclear halves joined by an ammonia or water molecule at the center through H-bonding. Each of the trinuclear halves is enantiopure but of opposite chirality to the other half, making the hexanuclear unit a meso isomer. Temperature dependent magnetic measurements showed the presence of ferromagnetic interactions among trinuclear Cu(II) units, a rare occurrence among trinuclear Cu(II) complexes. Characterization of the LiHL showed it to be enantiopure. Addition of a base, monitored using optical rotation, showed that racemization occurs as a result of base addition. The racemization depends on the base as well as the temperature. Base or Cu(II) induced racemization of amino acid derivatives has been indicated in a number of cases in the past but structural characterization of the products or formation of this type of chiral hexanuclear architecture was never reported. Structures of the complex and the ligand have a number of interesting H-bonding situations.

A simple spectrophotometric method for the determination of arsenic in industrial and environmental samples using 2,4-Dihydroxy benzophenone-2-amino thiophenol.

2,4-Dihydroxy benzophenone-2-amino thiophenol (BPBT) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of arsenic. The reagent reacts with arsenic in acidic medium (pH=6.0, sodium acetate-acetic acid buffer) to form light greenish yellow colored 1:1 (M:L) complex. Maximum absorbance was obtained at 343 nm and remains constant for over 24 h. The molar absorptivity and Sandell's sensitivity of BPBT are found to be 6.01×10(4) L mol(-1)cm(-1) and 0.0016 µg cm(-2) respectively. The system obeys Beer's law in the range of 0.125-2.637 µg/ml of As (III). Since BPBT method is more sensitive, it was applied for the determination of arsenic in some environmental water samples.

N-benzoate-N' salicylaldehyde ethynelediamine: a new fluorescent sensor for Zn2+ ion by "off-on" mode.

Imbalance of zinc ion (Zn(2+)) in human body causes diseases like Alzheimer's and Parkinson's and therefore Zn(2+) estimation in biological fluids has diagnostic values. Fluorescence "off-on" sensors have advantages of high sensitivity and in situ application over other sensors. A new fluorescent "off-on" Zn(2+) sensor, N-benzoate-N' salicylaldehyde ethynelediamine (L), has been synthesisied. In 1:1(v/v) CH3OH:PBS (PBS = phosphate buffer solution), L shows ca. 20 times enhancement in fluorescence intensity on interaction with Zn(2+), due to snapping of photoinduced electron transfer (PET) process, which is selective over metal ions - Na(+), K(+), Ca(2+), Ni(2+), Cu(2+), Cd(2+), Hg(2+) and Pb(2+). These metal ions either individually or all together does not interfere the sensing ability of L towards Zn(2+). A 1:1 interaction between L and Zn(2+) ion with binding constant 10(4.25) has been established from spectroscopic data.

Characterisation of Maillard reaction products derived from LEKFD--a pentapeptide found in ß-lactoglobulin sequence, glycated with glucose--by tandem mass spectrometry, molecular orbital calculations and gel filtration chromatography coupled with continuous photodiode array.

Maillard reaction peptides (MRPs) contribute to taste, aroma, colour, texture and biological activity. However, peptide degradation or the cross-linking of MRPs in the Maillard reaction has not been investigated clearly. A peptide of LEKFD, a part of ß-lactoglobulin, was heated at 110 °C for 24h with glucose and the reaction products were analysed by HPLC with ODS, ESI-MS, ESI-MS/MS and HPLC with gel-filtration column and DAD detector. In the HPLC fractions, an imminium ion of LEK*FD, a pyrylium ion or a hydroxymethyl furylium ion of LEK*FD, and KFD and EK were detected by ESI-MS. Therefore, those products may be produced by the Maillard reaction. The molecular orbital of glycated LEKFD at the lysine epsilon-amino residue with Schiff base form was calculated by MOPAC. HPLC with gel-filtration column showed cross-linking and degradation of peptides.

Primary amines protect against retinal degeneration in mouse models of retinopathies.

Vertebrate vision is initiated by photoisomerization of the visual pigment chromophore 11-cis-retinal and is maintained by continuous regeneration of this retinoid through a series of reactions termed the retinoid cycle. However, toxic side reaction products, especially those involving reactive aldehyde groups of the photoisomerized product, all-trans-retinal, can cause severe retinal pathology. Here we lowered peak concentrations of free all-trans-retinal with primary amine-containing Food and Drug Administration (FDA)-approved drugs that did not inhibit chromophore regeneration in mouse models of retinal degeneration. Schiff base adducts between all-trans-retinal and these amines were identified by MS. Adducts were observed in mouse eyes only when an experimental drug protected the retina from degeneration in both short-term and long-term treatment experiments. This study demonstrates a molecular basis of all-trans-retinal-induced retinal pathology and identifies an assemblage of FDA-approved compounds with protective effects against this pathology in a mouse model that shows features of Stargardt's disease and age-related retinal degeneration.

Probing the compound (E)-5-(diethylamino)-2-[(4-methylphenylimino)methyl]phenol mainly from the point of tautomerism in solvent media and the solid state by experimental and computational methods.

In this study, the molecular structure and spectroscopic properties of (E)-5-(diethylamino)-2-[(4-methylphenylimino)methyl]phenol were characterized experimentally by X-ray diffraction, FT-IR and UV-vis spectroscopic techniques and computationally by DFT method. It is concluded on the basis of X-ray diffraction and FT-IR analyses that the title compound exists in enol form in the solid state. UV-vis spectra of the title compound were recorded in different organic solvents to investigate the dependence of tautomerism on solvent types. The tautomerism-solvent relation was also studied by computational methods to have more insight on structural properties. The geometry optimization of the title compound in gas phase was performed by using DFT (B3LYP) method with 6-311G(d,p) basis set. The geometry optimizations in solvent media were carried out at the same theory level by the polarizable continuum model (PCM). In the calculation of excitation energies, TD-DFT calculations were carried out in both gas and solution phases. The computational investigation of non-linear optical properties indicates that the title compound has a good second order nonlinear optical property. The thermodynamic properties were obtained in the range of 100-500 K.

Antioxidant, electrochemical, thermal, antimicrobial and alkane oxidation properties of tridentate Schiff base ligands and their metal complexes.

In this study, two Schiff base ligands (HL(1) and HL(2)) and their Cu(II), Co(II), Ni(II), Pd(II) and Ru(III) metal complexes were synthesized and characterized by the analytical and spectroscopic methods. Alkane oxidation activities of the metal complexes were studied on cyclohexane as substrate. The ligands and their metal complexes were evaluated for their antimicrobial activity against Corynebacterium xerosis, Bacillus brevis, Bacillus megaterium, Bacillus cereus, Mycobacterium smegmatis, Staphylococcus aureus, Micrococcus luteus and Enterococcus faecalis (as gram-positive bacteria) and Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Yersinia enterocolitica, Klebsiella fragilis, Saccharomyces cerevisiae, and Candida albicans (as gram-negative bacteria). The antioxidant properties of the Schiff base ligands were evaluated in a series of in vitro tests: 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and reducing power activity of superoxide anion radical generated non-enzymatic systems. Electrochemical and thermal properties of the compounds were investigated.

Effects of osmotic pretreatments on oxidative stress, antioxidant profiles and cryopreservation of olive somatic embryos.

A three-day pretreatment of olive somatic embryos (SE) with 0.75 M sucrose, combined with cryoprotection (0.5M DMSO, 1M sucrose, 0.5M glycerol and 0.009 M proline) and controlled rate cooling, supported regrowth (as 34.6% fresh weight gain) and resumption of embryo development after cryopreservation. Pretreatment with mannitol or sorbitol did not support regrowth. Profiles of sugars, proline, antioxidant enzymes, Reactive oxygen species (ROS), secondary oxidation products and ethylene were constructed for the most successful (0.75 M) pretreatment series. Sucrose was the optimal pretreatment for supporting recovery, it also elevated glutathione reductase (GR) activity compared to controls, whereas superoxide dismutase (SOD), catalase and guaiacol peroxidase activities remained relatively unchanged. Superoxide dismutase activity was higher in SE pretreated with sucrose, compared with those pretreated with polyols; H(2)O(2) was enhanced in SE pretreated with sorbitol and sucrose compared to mannitol. The overall trend for ethylene and OH production revealed their levels were highest in SE pretreated with polyols albeit, for individual treatments this was not always the case. Generally, pretreatments did not significantly change embryo secondary oxidation profiles of ThioBarbituric Acid Reactive Substances (TBARS) and Schiff's bases. In combination these studies suggest oxidative processes may influence regrowth of cryopreserved olive SE and that optimal pretreatments could, in part, increase tolerance by an overall enhancement of endogenous antioxidants (particularly GR), proline and sugars.

Nutritional value and digestion rate of rhea meat proteins in association with storage and cooking processes.

The nutritional value of proteins was investigated after the storage and cooking of rhea M. Gastrocnemius pars interna. Oxidation of basic and aromatic amino acids, surface hydrophobicity and aggregation state of proteins, were determined in raw and cooked meat. In addition, myofibrillar proteins were exposed in vitro to proteases of the digestive tract. Cooking markedly affected the protein surface hydrophobicity. The BBP bound content was three times greater in cooked than in fresh rhea meat. A small increment in tryptophan content after cooking was observed. Storage influenced Schiff bases formation indicating the presence of protein-aldehyde adducts after cooking. High content of Schiff bases was found after cooking of samples stored for 5 days, demonstrating a probable implication of free amino groups, most likely from lysine. Cooking decreased the myofibrillar protein susceptibility to pepsin activity. After cooking, the proteolysis rate by pancreatic enzymes increased. Our findings support the importance of protein aggregation in the nutritional value of meat proteins.

Design, synthesis, growth and characterization of 4-methoxy-4'-dimethylamino-benzylidene aniline (MDMABA): a novel third order nonlinear optical material.

Synthesis, growth, X-ray crystal structure and characterization of a novel third order nonlinear optical material, 4-methoxy-4'-dimethylamino-benzylidene aniline (MDMABA), are reported for the first time. The asymmetric unit of MDMABA compound contains two crystallographically independent molecules (A and B), and they exist in the E-configuration. The structural perfection of the grown crystal is analyzed by high-resolution X-ray diffraction rocking curve analysis. The functional groups present in MDMABA are investigated by FTIR and FT-Raman spectral analyses. The placement of the protons is determined using HNMR spectrum. The range and percentage of optical transmission were ascertained by recording UV-vis-NIR spectrum. Thermal and mechanical properties are reported. Dielectric study shows that the dielectric constant of the crystal varies with frequency and temperature. The third order nonlinear optical absorption coefficient of the MDMABA crystal is determined by the Z-scan technique.

Evaluation of a Schiff base copper complex compound as potent anticancer molecule with multiple targets of action.

Copper is a biologically relevant metal as it is associated with various biomolecules related to essential physiological activities. Anticancer compounds with copper as a metal center is hypothesized to be less toxic and more potent. In the present study we have tested the efficacy of a family of Schiff base copper complexes of which the best compound was [Cu(Pyimpy)Cl(2)] where Pyimpy is a tridentate ligand containing two pyridine and one imine nitrogen donor. [Cu(Pyimpy)Cl(2)], represented as CuP1, was checked for its anticancer potential. The IC(50) value of CuP1 was found to be 4.29±0.42, 6.34±0.58 and 5.32±0.38 µM in MCF-7, PC3 and HEK 293 cells respectively. It was found to cause in vitro DNA fragmentation in comet assays and acridine orange staining of MCF 7 cells. CuP1 was further tested on rat breast tumor models and was found to inhibit tumor growth. It caused apoptosis within the tumor by the up regulation of caspase pathway and inhibition of the Akt, matrix metalloproteinase 9 and α-methyl acyl CoA racemase. Antioxidant enzymes which in general results in drug resistant condition in tumor tissues were significantly inhibited by this copper compound (P<0.05). Further, CuP1 did not show any prominent systemic toxicity. These results indicate that CuP1 can be a potential anticancer agent and further investigation will reveal more about its mode of action.

Effects of certain antioxidants on lipid peroxidation process in lung homogenates of L thyroxine-receiving rats.

OBJECTIVE: A possible role of antioxidants in thyreotoxicosis was investigated. We examined the parameters of lipid peroxidation (LPO): conjugated dienes (CD), malondialdehyde (MDA), Schiff bases (SB) in lung homogenates of male Wistar rats. METHODS: Two control groups were created: Group 1 - intact animals and Group 2 - animals injected with 0,9% NaCl. In Experiment I, the animals received L-thyroxin (LT4) i.p. (Groups 3-7). After one week the rats received additionally: Group 4 - melatonin (MEL); Group 5 - propylthiouracil (PTU); Group 6 - Ambroxol (AMB); Group 7 - N-acetylocysteine (NAC). In Experiment II, the animals received only antioxidants. RESULTS: In Experiment I, we noticed a significantly higher MDA and SB level in Group 2, compared to that in Group 1. Moreover, we observed a significantly higher MDA and SB level in Group 3, vs. that in Group 1, but SB level was lower in Group 3 than in Group 2. Melatonin, PTU and NAC reduced CD; PTU, AMB diminished MDA and MEL, AMB lowered SB levels as compared to Group 3. In Experiment II, we observed significantly higher MDA and SB level in Group 2, vs. that in Group 1. Melatonin, AMB and NAC decreased MDA and SB level, when compared to Group 2 but PTU elevated MDA and SB level vs. that in Group 1. CONCLUSIONS: 1) L-T4 suppresses LPO, 2) MEL, AMB and NAC protect against LPO, 3) PTU is an antioxidant in thyreotoxicosis, however, when administered alone, it enhances LPO, 4) stress accelerate LPO.