End Product Of Reaction Research Articles

Cyanidin-3-glucoside attenuates 4-hydroxynonenal- and visible light-induced retinal damage in vitro and in vivo.

4-Hydroxynonenal (HNE) is a highly reactive end-product of lipid peroxidation reaction that leads to retinal pigment epithelial (RPE) cell damage. Cyanidin-3-glucoside (C3G), the most abundant anthocyanin in the edible parts of plants, is a nutritional supplement used for preventing retinal damage. However, the protective effect of C3G against HNE-induced RPE cell damage remains to be elucidated. The protective mechanisms of C3G on ARPE-19 cells after HNE exposure were investigated in this study. Results showed that compared with HNE-treated cells, the viability of ARPE-19 cells was significantly (P < 0.05) increased after 1 and 5 μM C3G treatment. C3G exhibited a significant (P < 0.05) inhibitory effect on the expression of senescence-associated β-galactosidase in ARPE-19 cells. VEGF levels in the C3G groups were significantly (P < 0.05) decreased relative to those of the HNE-treated group. C3G also regulated the release of two inflammatory mediators, namely monocyte chemoattractant protein 1 and interleukine-8, in ARPE-19 cells after HNE treatment. Furthermore, C3G attenuated retinal cell apoptosis in pigmented rabbits induced by visible light. Therefore, our data showed that C3G has efficient protective effects on HNE-induced apoptosis, angiogenesis, and dysregulated cytokine production in ARPE-19 cells.

Dietary Amino Acids and the Gut-Microbiome-Immune Axis: Physiological Metabolism and Therapeutic Prospects.

Dietary amino acids (AAs) are not only absorbed and metabolized by enterocytes but also available to the microbiota in the gut in mammals. In addition to serving as the materials for protein synthesis, AAs can act as precursors for numerous metabolic end products in reactions involving the intestinal mucosa and microbiota. After penetrating the epithelial barrier, microbial metabolites can enter and accumulate in the host circulatory system, where they are sensed by immune cells and then elicit a wide range of biological functions via different receptors and mechanisms. Some intestinal bacteria can also synthesize certain AAs, implying that the exchange of AAs between hosts and microorganisms is bidirectional. Changes in AA composition and abundance can affect AA-metabolizing bacterial communities and modulate macrophages and dendritic cells via toll-like receptors (TLRs), autoinducer-2 (AI-2), and NOD-like receptors (NLRs), and also regulate the gut-microbiome-immune axis via aryl hydrocarbon receptor (AhR), serotonin/5-hydroxytryptamine (5-HT), and other signaling pathways, all of which play critical roles in regulating the intestinal mucosal immunity and microbiota directly or indirectly, contributing to intestinal homeostasis. Therefore, the current findings of the effects of certain functional AAs on the gut-microbiome-immune axis are reviewed, illustrating signaling pathways of tryptophan (Trp), glutamine (Gln), methionine (Met), and branched-chain AAs (BCAAs) in the intestinal barrier and regarding immunity via crosstalk with their receptors or ligands. These findings have shed light on the clinical applications of dietary AAs in improving gut microbiota and mucosal immunity, therefore benefiting the gut as well as local and systemic health.

Distribution of nadph-diaphorase positive structures of olfactory bulb of rats in ontogenesis

Aim: to identify peculiarities of distribution of NADPH-diaphorase (NADPH-d) positive structures in olfactory bulbs of rats of different age.&#x0D; Materials and Methods. The study was conducted on 22 white male rats. The object of research was olfactory bulbs of newborn rats – 1-3 days, suckling period – 7, 14, 21 days, infantile – 30 days, juvenile – 60, and mature – 180 days. The study was conducted on cryostat serial sections of olfactory bulbs (20 µm). Nitroxidergic structures were identified by histochemical labelling of NADPH-d (by Hope method). In a standard section, the area of NADPH-diaphorase-positive cells (100 in each case), surface area of glomeruli, the number of positive neurons surrounding a glomerulus, were measured.&#x0D; Results. In result of study it was found that in the olfactory bulb of rats of the studied age only groups of superficial and deep short-axon neurons and periglomerular neurons showed positivity to NADPH-d. The end product of reaction was distributed in somas and extensions of a part of cells with the density of distribution depending on the layer of the olfactory bulb and on the age of animals. Besides, positivity to the enzyme was also found in the central parts of glomeruli with distribution of diaphorase depending not on age, but rather on localization of glomeruli.&#x0D; Conclusion. Age-related transformations of positive subpopulation of neurons of olfactory bulb indicate active participation of NO in the processes of postnatal differentiation, growth and development of olfactory bulb.

Distribution of nadph-diaphorase positive structures of olfactory bulb of rats in ontogenesis

Aim: to identify peculiarities of distribution of NADPH-diaphorase (NADPH-d) positive structures in olfactory bulbs of rats of different age.&#x0D; Materials and Methods. The study was conducted on 22 white male rats. The object of research was olfactory bulbs of newborn rats – 1-3 days, suckling period – 7, 14, 21 days, infantile – 30 days, juvenile – 60, and mature – 180 days. The study was conducted on cryostat serial sections of olfactory bulbs (20 µm). Nitroxidergic structures were identified by histochemical labelling of NADPH-d (by Hope method). In a standard section, the area of NADPH-diaphorase-positive cells (100 in each case), surface area of glomeruli, the number of positive neurons surrounding a glomerulus, were measured.&#x0D; Results. In result of study it was found that in the olfactory bulb of rats of the studied age only groups of superficial and deep short-axon neurons and periglomerular neurons showed positivity to NADPH-d. The end product of reaction was distributed in somas and extensions of a part of cells with the density of distribution depending on the layer of the olfactory bulb and on the age of animals. Besides, positivity to the enzyme was also found in the central parts of glomeruli with distribution of diaphorase depending not on age, but rather on localization of glomeruli.&#x0D; Conclusion. Age-related transformations of positive subpopulation of neurons of olfactory bulb indicate active participation of NO in the processes of postnatal differentiation, growth and development of olfactory bulb.

Management of Diabetes Mellitus with Puerarin, a Natural Isoflavone From Pueraria lobata.

Diabetes mellitus (DM) has become one of the most challenging public health problems globally. The increasing prevalence and mortality rates call for more effective therapeutic agents, especially for DM complications. Traditional herbs have a long clinical application history for DM treatment. Puerarin is a natural isoflavone from Pueraria lobata (Wild.) Ohwi which has been consumed both as a functional food and herb in Eastern Asia countries. Documented data has shown that puerarin has cardio-protective, neuroprotective, anti-oxidative, anti-inflammatory and many other effects. In this review, we will summarize the beneficial effects and underlying mechanisms of puerarin on DM and complications. Puerarin may directly benefit DM by decreasing blood glucose levels, improving insulin resistance, protecting islets, inhibiting inflammation, decreasing oxidative stress and inhibiting Maillard reaction and advanced glycation end products (AGEs) formation. Furthermore, puerarin may also benefit DM indirectly by retarding and improving a series of DM complications, such as cardiovascular complications, diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, etc. However, comprehensive studies of its effect and mechanisms are needed. In addition, its efficacy is relatively low, which is partially due to its pharmacokinetics profiles. Though puerarin shows low toxicity to experimental animals, its safety on human remains to be clarified. Collectively, we suggest that puerarin might be a potential adjuvant agent for the treatment of DM and DM complications in future.

Enzymatic and molecular characterization of an acidic and thermostable chitinase 1 from Streptomyces thermodiastaticus HF 3-3.

Chitinase 1 (Chi1) is an acidic and thermostable hydrolytic enzyme capable of the breakdown of chitin, a resilient biopolymer that is the primary building block of fungi cell walls and marine exoskeletons. In this study, Chi1 was purified from the bacterium Streptomyces thermodiastaticus HF 3-3, and its properties were carefully characterized. The molecular mass of Chi1 was estimated to be approximately 46 kDa and, through sequencing, its N-terminal amino acid sequence was identified as ADSGKVKL. Although the optimal operating temperature and pH for Chi1 were determined to be 65°C and pH 5.5, respectively, the purified enzyme was stable over wide pH (1.5-9) and temperature ranges. Moreover, Chi1 retained 87% of its activity in the presence of 15% NaCl. While Chi1 activity was inhibited by Ag+ and Mn2+, other chemicals tested had no significant effect on its enzymatic activity. The Km and Vmax values of Chi1 for the substrate colloidal chitin were 1.23 ± 0.7 mg/mL and 6.33 ± 1.0 U/mg, respectively. Thin-layer chromatography analysis of the enzymatic reaction end products mainly detected diacetylchitobiose. We also cloned the Chi1 gene and purified the recombinant protein; the properties of the recombinant enzyme were nearly identical to those of the native enzyme. Therefore, Chi1 purified from S. thermodiastaticus HF 3-3 is unique, as it is highly stable under broad range of pH values, temperatures, and chemical exposures. Combined, these properties make this enzyme attractive for use in the industrial bioconversion of chitin.

Re-engineering of Bacterial Luciferase; For New Aspects of Bioluminescence.

Bacterial luminescence is the end-product of biochemical reactions catalyzed by the luciferase enzyme. Nowadays, this fascinating phenomenon has been widely used as reporter and/or sensors to detect a variety of biological and environmental processes. The enhancement or diversification of the luciferase activities will increase the versatility of bacterial luminescence. Here, to establish the strategy for luciferase engineering, we summarized the identity and relevant roles of key amino acid residues modulating luciferase in Vibrio harveyi, a model luminous bacterium. The current opinions on crystal structures and the critical amino acid residues involved in the substrate binding sites and unstructured loop have been delineated. Based on these, the potential target residues and/or parameters for enzyme engineering were also suggested in limited scale. In conclusion, even though the accurate knowledge on the bacterial luciferase is yet to be reported, the structure-guided site-directed mutagenesis approaches targeting the regulatory amino acids will provide a useful platform to re-engineer the bacterial luciferase in the future.

Development of Ratiometric Fluorescent Biosensors for the Determination of Creatine and Creatinine in Urine.

In this study, the oxazine 170 perchlorate (O17)-ethylcellulose (EC) membrane was successfully exploited for the fabrication of creatine- and creatinine-sensing membranes. The sensing membrane exhibited a double layer of O17-EC membrane and a layer of enzyme(s) entrapped in the EC and polyurethane hydrogel (PU) matrix. The sensing principle of the membranes was based on the hydrolytic catalysis of urea, creatine, and creatinine by the enzymes. The reaction end product, ammonia, reacted with O17-EC membrane, resulting in the change in fluorescence intensities at two emission wavelengths (λem = 565 and 625 nm). Data collected from the ratio of fluorescence intensities at λem = 565 and 625 nm were proportional to the concentrations of creatine or creatinine. Creatine- and creatinine-sensing membranes were very sensitive to creatine and creatinine at the concentration range of 0.1–1.0 mM, with a limit of detection (LOD) of 0.015 and 0.0325 mM, respectively. Furthermore, these sensing membranes showed good features in terms of response time, reversibility, and long-term stability. The interference study demonstrated that some components such as amino acids and salts had some negative effects on the analytical performance of the membranes. Thus, the simple and sensitive ratiometric fluorescent sensors provide a simple and comprehensive method for the determination of creatine and creatinine concentrations in urine.

(Invited) Ethanol Photoreaction over Anatase TiO2(101) and Rutile TiO2(110) Single Crystals. A Combined STM and Online Mass Spectrometry

The reactions of ethanol have been investigated over anatase TiO2(101) and rutile TiO2 (110) single crystals by STM and on-line mass spectrometry to determine the adsorbate species in the dark and post UV illumination, in the presence and absence of O2 or Au nanoclusters, in order to extract initial reaction parameters under photo-excitation. On anatase (101) TiO2 single crystal the reaction rate for the photo-oxidation of ethanol to acetaldehyde is found to be strongly dependent on O2 partial pressures and surface coverage with an order of the reaction for O2 close to 0.15. Carbon-carbon bond dissociation leading to CH3 radicals in the gas phase was found to be a minor pathway, which is contrary to the case of TiO2 rutile (110) single crystal, as previously reported by our group and others. Our STM images distinguished two types of surface adsorbates upon ethanol exposure that can be attributed to its molecular and dissociative modes. Upon UV exposure at (and above) 3×10-8 mbar O2, a third species is identified as a reaction end-product, which can be tentatively attributed to acetate/formate species, in line with XPS C1s measurements. The room temperature photo-oxidation of ethanol has also been investigated over a rutile TiO2(110) single crystal by STM and on-line mass spectrometry, in the presence of O2 to determine adsorbate species remaining post UV exposure and emitted gas phase products. In addition to acetaldehyde, methyl radical was detected in the mass spectrometry resulting from the photo-fragmentation of an acetaldehyde-O complex. Formic acid species bound to Ti5c in a bi-dentate mode were identified by STM on the surface after the reaction. The effect of O2 partial pressure on the reaction selectivity demonstrated a dominance of the photo-fragmentation process with increasing pressure unlike the case of anatase TiO2(101) single crystal. In addition the effect of Au particles on the reaction of the TiO2(110 rutile has been investigated for hydrogen production under photo-irradiation in UHV conditions. It was found that particle size in the range 4 to 8 nm do not change the reaction rate yet particle density does. Detailed reaction mechanism for both reduction and oxidation reactions are addressed based on structural and kinetic information from the UHV systems and compared to those of their corresponding powder forms in liquid-solid photocatalytic reactions conditions.

Abstract P4-07-05: MicroRNA-27b mediates deregulation of energy metabolism in breast cancer

Abstract MicroRNAs (miRNAs) are a class of small, non-coding RNA which participate in gene regulation by targeted silencing of specific mRNA transcripts. Recently, it has become clear that dysfunctional miRNA expression is an important contributor to the deregulation of key signaling pathways underlying carcinogenesis. MicroRNA-27b is an example of one such pro-oncogenic miRNA, and correspondingly, its expression has been found to be upregulated in breast cancer cells and tissues. In this regard, several targets of miR-27b have previously been verified, and implicate miR-27b in multiple neoplastic processes including migration, invasion and metastasis. In order to enable future development of miRNA-based cancer therapies, the putative targets of each miRNA must be mapped more comprehensively. Such awareness is necessary in order to make informed choices regarding whether a miRNA-based therapy is likely to be effective and what side-effects should be anticipated. Therefore, this project seeks to further establish the role of miR-27b in the context of breast cancer, specifically by identifying novel target transcripts under its control. Using target prediction algorithms and breast cancer cell culture models, initial evidence has implicated Pyruvate Dehydrogenase Protein X (PDHX) to be a probable target. As a structural component of the Pyruvate Dehydrogenase Complex, the role of PDHX in linking the end products of glycolytic reactions with subsequent oxidative phosphorylation pathways is indispensable. However, a hallmark of cancer cell metabolism is the propensity to consume glucose aerobically, which liberates additional carbon skeletons for use in biosynthetic reactions that are crucial for tumor growth. In this way, miR-27b overexpression appears to sever the link between glycolysis and subsequent catabolic pathways, thus conferring a pro-growth advantage to the cancer cells. Expression profiling of PDHX using both breast cancer cell lines and human breast tissues (which overexpress miR-27b) reveal that PDHX levels are indeed significantly reduced, thus supporting the notion that miR-27b alters cancer cell metabolism specifically by targeting this gene in breast cancer. Improving the current understanding of miR-27b's functions will lay the necessary ground work to evaluate its potential as a novel target for cancer therapy. Similarly, the awareness of the expression status of miR-27b and its targets in breast cancer tumors will further efforts to find suitable miRNA tissue biomarkers to enhance screening and prognosis. In this way, microRNA-based approaches offer the distinct potential to improve cancer detection as well as treatment, making them a dynamic method to improve management of breast cancer patients in the future. Citation Format: Eastlack SC, Alahari SK, Dong S, Cole JT. MicroRNA-27b mediates deregulation of energy metabolism in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-07-05.

A sensitive single-enzyme assay system using the non-ribosomal peptide synthetase BpsA for measurement of L-glutamine in biological samples

The ability to rapidly, economically and accurately measure L-glutamine concentrations in biological samples is important for many areas of research, medicine or industry, however there is room for improvement on existing methods. We describe here how the enzyme BpsA, a single-module non-ribosomal peptide synthetase able to convert L-glutamine into the blue pigment indigoidine, can be used to accurately measure L-glutamine in biological samples. Although indigoidine has low solubility in aqueous solutions, meaning direct measurements of indigoidine synthesis do not reliably yield linear standard curves, we demonstrate that resolubilisation of the reaction end-products in DMSO overcomes this issue and that spontaneous reduction to colourless leuco-indigoidine occurs too slowly to interfere with assay accuracy. Our protocol is amenable to a 96-well microtitre format and can be used to measure L-glutamine in common bacterial and mammalian culture media, urine, and deproteinated plasma. We show that active BpsA can be prepared in high yield by expressing it in the apo-form to avoid the toxicity of indigoidine to Escherichia coli host cells, then activating it to the holo-form in cell lysates prior to purification; and that BpsA has a lengthy shelf-life, retaining >95% activity when stored at either −20 °C or 4 °C for 24 weeks.

Transglycosylation reactions, a main mechanism of phenolics incorporation in coffee melanoidins: Inhibition by Maillard reaction.

Under roasting conditions, polysaccharides depolymerize and also are able to polymerize, forming new polymers through non-enzymatic transglycosylation reactions (TGRs). TGRs can also occur between carbohydrates and aglycones, such as the phenolic compounds present in daily consumed foods like coffee. In this study, glycosidically-linked phenolic compounds were quantified in coffee melanoidins, the polymeric nitrogenous brown-colored compounds formed during roasting, defined as end-products of Maillard reaction. One third of the phenolics present were in glycosidically-linked form. In addition, the roasting of solid-state mixtures mimicking coffee beans composition allowed the conclusion that proteins play a regulatory role in TGRs extension and, consequently, modulate melanoidins composition. Overall, the results obtained showed that TGRs are a main mechanism of phenolics incorporation in melanoidins and are inhibited by amino groups through Maillard reaction.

Stabilization of whey protein isolate (WPI) through interactions with sugar beet pectin (SBP) induced by controlled dry-heating

It has been shown previously that reacting whey protein isolate (WPI) with sugar beet pectin (SBP) through a Maillard type reaction in a dry-state led to noticeable improvement in the physical, chemical and functional properties of the end products. Studies on the changes in the molecular structure of whey protein as a result of the reaction were carried out in this work to provide a molecular understanding of these observed improvements. The effect of interacting and conjugating with SBP on the apparent secondary structure of WPI was examined by far-UV circular dichroism (CD) spectroscopy and followed by spectral deconvolution. Results showed that the structure of WPI, especially the antiparallel β-sheet element, was preserved by reacting with SBP at the weight ratios of WPI:SBP = 3:1, 2:1, and 1:1. The analysis of difference UV-VIS spectra indicated significant changes occurred in the molecular electronic states of both WPI and the feruloyl moieties of SBP. Initial Maillard reaction products were detected in the form of the FRET complexes with WPI as the donor, and SBP, the acceptor by the studies of the steady-state fluorescence and the lifetime of the excited states. The tertiary structural contacts in WPI, probed by the intrinsic Trp fluorescence, were disrupted significantly upon reacting with SBP at an equal ratio (1:1). The thermal stability of WPI, however, at both secondary and tertiary structural levels, was greatly improved by the dry-heating induced reaction with SBP at all levels. The thermal stability of the feruloyl groups of SBP was also enhanced by reacting with WPI. Furthermore, the fluorescence lifetime studies definitively identified the distinctive advanced Maillard reaction end products (AMREPs) formed between WPI and SBP at varying ratios.

Inhibitory effect of sugarcane molasses extract on the formation of Nε-(carboxymethyl)lysine and Nε-(carboxyethyl)lysine.

Molasses, the main byproduct of sugar production, is a well-known source of phenolic compounds. In this study, the effect of sugarcane molasses extract on the formation of Nε-(carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) was investigated in glucose-lysine model reaction systems. Results showed that sugarcane molasses extract significantly and dose dependently inhibited the formation of CML and CEL in model reaction systems. The antiglycation activities of sugarcane molasses extract were not only brought about by its antioxidant activities but also associated with its trapping abilities of reactive carbonyl species, such as glyoxal (GO) and methylglyoxal (MGO), the key intermediate compound for the formation of CML and CEL. Besides, the presence of sugarcane molasses extract effectively reduced the extent of browning. The present study emphasized the potential health effects of sugarcane molasses and the possibility of using byproducts as effective ingredients to reduce dietary Maillard reaction end products.

Deciphering characteristics of the designer cellulosome from Bacillus subtilis WB800N via enzymatic analysis

Recombinant Bacillus subtilis WB800N harboring pGETS 118 designer cellulosome genes was applied to the artificial cellulosome production. To investigate the characteristics of cellulosome assembly in the supernatant, three free enzymes clones, i.e., endoglucanase, exoglucanase and xylanase, were constructed. The samples of the respective free enzymes and the cellulosome were collected and examined via various enzymatic assays. In comparison of specific activity of anchored cellulosome and the free enzymes on cell pellets, it was found that only anchored cellulosome exhibited the activities. No activity was detected on the cell pellets of the three free enzyme clones. This indicated that the designer cellulosome subunits must be properly self-assembled into a substantial complex capable of the cellulose degradation. To study the cellulose hydrolytic behavior, the best specific activities of endoglucanase and xylanase obtained in the supernatant cellulosome were 3.62±0.02U/mg and 1.97±0.06U/mg, respectively. The end products of the enzyme reaction detected via HPLC analysis showed that oligosaccharide and cellobiose were the major products in the hydrolytic reactions. In the kinetic studies, the Vmax value (8.98mM/h) for endoglucanase in the supernatant cellulosome was higher than pellets (0.603mM/h). However, the endoglucanase of pellets gave a lower Km value of 0.359g/L, indicating a higher substrate affinity than that in the supernatant (11.87g/L).

Ambient light-based optical biosensing platform with smartphone-embedded illumination sensor

We present a hand-held optical biosensing system utilizing a smartphone-embedded illumination sensor that is integrated with immunoblotting assay method. The smartphone-embedded illumination sensor is regarded as an alternative optical receiver that can replaces the conventional optical analysis apparatus because the illumination sensor can respond to the ambient light in a wide range of wavelengths, including visible and infrared. To demonstrate the biosensing applicability of our system employing the enzyme-mediated immunoblotting and accompanying light interference, various types of ambient light conditions including outdoor sunlight and indoor fluorescent were tested. For the immunoblotting assay, the biosensing channel generating insoluble precipitates as an end product of the enzymatic reaction is fabricated and mounted on the illumination sensor of the smartphone. The intensity of penetrating light arrives on the illumination sensor is inversely proportional to the amount of precipitates produced in the channel, and these changes are immediately analyzed and quantified via smartphone software. In this study, urinary C-terminal telopeptide fragment of type II collagen (uCTX-II), a biomarker of osteoarthritis diagnosis, was tested as a model analyte. The developed smartphone-based sensing system efficiently measured uCTX-II in the 0–5ng/mL concentration range with a high sensitivity and accuracy under various light conditions. These assay results show that the illumination sensor-based optical biosensor is suitable for point-of-care testing (POCT).

Evolution of protein bound Maillard reaction end-products and free Amadori compounds in low lactose milk in presence of fructosamine oxidase I

Thermal treatments and storage influence milk quality, particularly in low lactose milk as the higher concentration of reducing sugars can lead to the increased formation of the Maillard reaction products (MRPs). The control of the Amadori products (APs) formation is the key step to mitigate the Maillard reaction (MR) in milk. The use of fructosamine oxidases, (Faox) provided promising results. In this paper, the effects of Faox I were evaluated by monitoring the concentration of free and bound MRPs in low lactose milk during shelf life. Results showed that the enzyme reduced the formation of protein-bound MRPs down to 79% after six days at 37°C. Faox I lowered the glycation of almost all the free amino acids resulting effective on basic and polar amino acids. Data here reported corroborate previous findings on the potentiality of Faox enzymes in controlling the early stage of the MR in foods.

Pcal_0768, a hyperactive 4-α-glucanotransferase from Pyrobacculum calidifontis.

Genome sequence of hyperthermophilic archaeon Pyrobaculum calidifontis revealed the presence of an open reading frame, Pcal_0768, corresponding to a putative 4-α-glucanotranferase belonging to glycoside hydrolases (GH) family 77. We have produced, in Escherichia coli, and purified recombinant Pcal_0768 which exhibited high disproportionation (690Umg(-1)) activity. To the best of our knowledge, this is the highest ever reported activity for any member of family GH77. Maltooligosaccharides, when used as sole substrates, were disproportionated into linear maltooligohomologues. The analysis of the reaction end products revealed no evidence for the production of cycloamyloses. Catalytic activity of the enzyme remained unchanged in the presence or the absence of ionic and nonionic detergents. γ-cyclodextrin, an inhibitor of 4-α-glucanotransferases, did not show any inhibitory effect on Pcal_0768 activity. These properties make Pcal_0768 a potential candidate for starch processing industry.

Facile Synthesis of Tributyrin Catalyzed by Versatile Sulfated Iron Oxide: Reaction Pathway and Kinetic Evaluation

Tributyrin, the triglyceride ester, exhibits strong properties as inhibitor of cancer cell growth in both humans and animals, which can increase the shelf life of drug. In this paper, tributyrin was synthesized by esterification reaction of butanoic acid with glycerol catalyzed by a low cost, ecofriendly green catalyst sulfated iron oxide. Effect of varying catalyst loading, stirring speed, and temperature on initial reaction rate was investigated. Reaction kinetics and adsorption and thermodynamic parameters were determined by evaluating the effect of concentration of butanoic acid, glycerol, and water addition on reaction rate. Eley–Rideal model using activity coefficients was employed to account for nonideality of the system to elucidate the experimental data. A maximal acid conversion of 91.8% was obtained at the temperature of 448.15 K. Activation energy was calculated to be 25.348 kJ/mol. The end product of reaction was characterized by means of thin layer chromatography (TLC), Fourier transform inf...

Protective Effect of Sinapine against Hydroxyl Radical-Induced Damage to Mesenchymal Stem Cells and Possible Mechanisms.

As a phenolic alkaloid occurring in Cruciferous plants, sinapine was observed to protect mesenchymal stem cells (MSCs) against ·OH-induced damage in this study. It was also found to prevent DNA from damage, to scavenge various free radicals (·OH, ·O2(-), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt) (ABTS)(+·), and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·)), and to reduce Cu(2+) to Cu(+). To further explore the mechanism, the end-product of sinapine reaction with DPPH· was determined using HPLC-electrospray ionization (ESI)-MS/MS and HPLC-diode array detector (DAD). Four molecular ion peaks (m/z 701, 702, 703, and 351) in HPLC-ESI-MS/MS analysis indicated a radical adduct formation (RAF) pathway; while a bathochromic shift (λ(max) 334→475 nm) in HPLC-DAD indicated the formation of quinone as the oxidized product of the phenolic -OH group. Based on these results, it may be concluded that, (i) sinapine can effectively protect against ·OH-induced damage to DNA and MSCs; such protective effect may provide evidence for a potential role for sinapine in MSC transplantation therapy, and be responsible for the beneficial effects of Cruciferous plants. (ii) The possible mechanism for sinapine to protect against ·OH-induced oxidative damage is radical-scavenging, which is thought to be via hydrogen atom (H·) transfer (HAT) (or sequential electron (e) proton transfer (SEPT))→RAF pathways.