Inhibition of β-galactosidases with mono- and disaccharides

It was demonstrated that, in reactions of the hydrolysis of model substrate 2-nitrophenyl-β-D-galactopyranoside (2-NPGP) monosaccharides D-fructose and D-xylose with hydroxyl substituents oppositely directed at the neighboring carbon atoms in the furan ring, as in D-glucose, act as noncompetitive inhibitors of β-galactosidase from E. coli; for mushroom, β-galactosidases from P. canescens and A. oryzae D-galactose is a stronger inhibitor. It was also found that the inhibition constant is the highest in the case of the most active enzyme (E. coli) and is the lowest for the least active one (P. canescens).     

An improved procedure for the synthesis of N-bromoacetyl-β-glycopyranosylamines, derivatives of mono- and disaccharides

An improved procedure for the synthesis of N-bromoacetyl--glycopyranosylamines from the corresponding -glycosylamines was developed. The procedure is applicable to a wide range of derivatives of monosaccharides (hexoses, 2-acetamido-2-deoxyhexoses, hexuronamides, and 6-deoxyhexoses) and some disaccharides. For the derivatives of pentoses and 2-deoxyhexoses, the use of the corresponding -glycosylammonium carbamates was found to be more convenient. N-Bromoacetyl--glycopyranosylamines derived from D-mannose, L-rhamnose, D-glucuronamide, 2-deoxy-D-arabino-hexose, 2-deoxy-D-lyxo-hexose, and melibiose were obtained for the first time.     

N-glycyl-β-glycopyranosylamines, derivatives of mono- and disaccharides, and their use for the preparation of carboxylic acid glycoconjugates

A convenient preparative procedure was developed for the synthesis ofN-glycyl-β-glycopyranosylamines, derivatives of monosaccharides (d-galactose,d-mannose,l-fucose, andN-acetyl-d-glucosamine) and disaccharides (lactose, melibiose, cellobiose, and maltose). These compounds were demonstrated to be useful for the preparation of glycoconjugates of biologically active compounds containing the carboxy group (nicotinic, orotic, kynurenic, and indoleacetic acids). Synthetic pathways were developed for conversions ofN-glycyl-β-glycopyranosylamines into derivatives containing the carboxy group with the use of malonic andl-tartaric acid derivatives. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1461–1466, August, 2000.     

Preparation and methodology for chemical mapping of sol–gel thin films containing lysozyme

Sol–gels are seeing widespread interest as suitable materials for the immobilization of biomolecules in applications ranging from optical coatings to specialty biocatalysts. Although there are numerous studies that have characterized these materials in terms of their macroscopic properties, few studies have examined and correlated these properties at the microscopic level. This study describes a spin-coating technique for the preparation of aluminum-supported sol–gel thin films containing immobilized lysozyme [E.C. 3.2.1.17] that are suitable for chemical mapping using FTIR microscopy operating in reflectance mode. This type of information can then be used to understand a variety of aspects of these materials which can be used for optimal engineering of these materials, as well as insightful design and modeling. A data analysis method was developed to extract information on chemical speciation and domain information on the materials from FTIR data matrices. Results from these studies indicated that, contrary to what might be expected, these sol–gels are not homogeneous on the microscopic level. Instead, they are heterogeneous in both the distribution of lysozyme and hydrophobic monomers at the scale investigated (20 μm resolution). The method described here has promise in terms of providing a non-invasive approach of chemically mapping concentrations of proteinaceous and related substances as well as chemical domains in situ in sol–gel thin films.     

Hydrolysis of cellobiose catalyzed by zeolites—the role of acidity and micropore structure

The roles of acidity and micropore structure of zeolite were studied in the hydrolysis of the model oligosaccharide of cellulose–cellobiose. HZSM-5, HY, HMOR and Hβ zeolites were selected as model catalysts for the hydrolysis of cellobiose. The effect of acidity of zeolite, including the strength, type and location, on its catalytic activity was investigated. The strong Br?nsted acid sites located in micropores are the active sites for the hydrolysis of cellobiose to glucose. Meanwhile, the catalytic performance of zeolite is also dependent on the micropore size of zeolite.     

Low-Fouling Fluoropolymers for Bioconjugation and In Vivo Tracking

The conjugation of hydrophilic low-fouling polymers to therapeutic molecules and particles is an effective approach to improving their aqueous stability, solubility, and pharmacokinetics. Recent concerns over the immunogenicity of poly(ethylene glycol) has highlighted the importance of identifying alternative low fouling polymers. Now, a new class of synthetic water-soluble homo-fluoropolymers are reported with a sulfoxide side-chain structure. The incorporation of fluorine enables direct imaging of the homopolymer by ¹⁹F MRI, negating the need for additional synthetic steps to attach an imaging moiety. These self-reporting fluoropolymers show outstanding imaging sensitivity and remarkable hydrophilicity, and as such are a new class of low-fouling polymer for bioconjugation and in vivo tracking.     

Synthesis of two derivatives of tigogenyl disaccharides containing N-acetylglucosamine and the long range shielding effect of benzoyl groups

Two tigogenyl glycosides containing N-acetylglucosamine were synthesized.Their structures were confirmed by1H and13CNMR spectra.The shielding effect caused by benzoyl groups was elucidated by1H NMR,COSY,HSQC,HMBC spectroscopy.     

sp2-Iminosugar O-, S-, and N-glycosides as conformational mimics of α-linked disaccharides; implications for glycosidase inhibition

The synthesis of mimics of the α(1→6)- and α(1→4)-linked disaccharides isomaltose and maltose featuring a bicyclic sp(2)-iminosugar nonreducing moiety O-, S-, or N-linked to a glucopyranoside residue is reported. The strong generalized anomeric effect operating in sp(2)-iminosugars determines the α-stereochemical outcome of the glycosylation reactions, independent of the presence or not of participating protecting groups and of the nature of the heteroatom. It also imparts chemical stability to the resulting aminoacetal, aminothioacetal, or gem-diamine functionalities. All the three isomaltose mimics behave as potent and very selective inhibitors of isomaltase and maltase, two α-glucosidases that bind the parent disaccharides either as substrate or inhibitor. In contrast, large differences in the inhibitory properties were observed among the maltose mimics, with the O-linked derivative being a more potent inhibitor than the N-linked analogue; the S-linked pseudodisaccharide did not inhibit either of the two target enzymes. A comparative conformational analysis based on NMR and molecular modelling revealed remarkable differences in the flexibility about the glycosidic linkage as a function of the nature of the linking atom in this series. Thus, the N-pseudodisaccharide is more rigid than the O-linked derivative, which exhibits conformational properties very similar to those of the natural maltose. The analogous pseudothiomaltoside is much more flexible than the N- or O-linked derivatives, and can access a broader area of the conformational space, which probably implies a strong entropic penalty upon binding to the enzymes. Together, the present results illustrate the importance of taking conformational aspects into consideration in the design of functional oligosaccharide mimetics.     

Synthesis and Antitumor Activities In Vitro of Solanesylpiperazinotriamine

Chemotherapy is one of the most important treatments of cancer, however, clinical use of conventional anticancer drugs is often limited by their side effects such as toxicity for normal tissues and multidrug resistance of tumor cells1, 2. Because of the s…     

The density and surface tension of In–Sn and Cu–In–Sn alloys

Abstract  

The density and surface tension of binary In–Sn and ternary Cu–In–Sn alloys have been measured by a sessile-drop method. Decrease of the density and of the surface tension was observed with rising temperature. With increased Sn content in the alloys, the density increased while the surface tension reduced slightly. Addition of Cu could significantly increase the density and surface tension in the Cu–In–Sn system. The surface tension of the Cu–In–Sn alloys was also calculated by means of Butler’s equation, and compared with experimental values, showing good agreement.     

Synthesis of Sug1-4GalNAcα disaccharides and their interaction with human blood antibodies

Disaccharides Sug1-4GalNAcα-Osp (Sug = Gal, Glc, GalNAc, GlcNAc in α- or β-configuration) were synthesized as spacer (sp) glycosides. Their strong interaction with serum antibodies of healthy donors was demonstrated using a printed glycan array (PGA).     

The Use of MALDI-TOF-MS and In Silico Studies for Determination of Antimicrobial Peptides’ Affinity to Bacterial Cells

Several methods have been proposed for determining the binding affinity of antimicrobial peptides (AMPs) to bacterial cells. Here the utilization of MALDI-TOF-MS was proposed as a reliable and efficient method for high throughput AMP screening. The major advantage of the technique consists of finding AMPs that are selective and specific to a wide range of Gram-negative and -positive bacteria, providing a simple reliable screening tool to determine the potential candidates for broad spectrum antimicrobial drugs. As a prototype, amp-1 and -2 were used, showing highest activity toward Gram-negative and -positive membranes respectively. In addition, in silico molecular docking studies with both peptides were carried out for the membranes. In silico results indicated that both peptides presented affinity for DPPG and DPPE phospholipids, constructed in order to emulate an in vivo membrane bilayer. As a result, amp-1 showed a higher complementary surface for Gram-negative while amp-2 showed higher affinity to Gram-positive membranes, corroborating MS analyses. In summary, results here obtained suggested that in vitro methodology using MALDI-TOF-MS in addition to theoretical studies may be able to improve AMP screening quality.     

Synchrotron-based FTIR microspectroscopy for the mapping of photo-oxidation and additives in acrylonitrile–butadiene–styrene model samples and historical objects

Synchrotron-based Fourier transform infrared micro-spectroscopy (SR-μFTIR) was used to map photo-oxidative degradation of acrylonitrile–butadiene–styrene (ABS) and to investigate the presence and the migration of additives in historical samples from important Italian design objects. High resolution (3 × 3 μm²) molecular maps were obtained by FTIR microspectroscopy in transmission mode, using a new method for the preparation of polymer thin sections. The depth of photo-oxidation in samples was evaluated and accompanied by the formation of ketones, aldehydes, esters, and unsaturated carbonyl compounds. This study demonstrates selective surface oxidation and a probable passivation of material against further degradation. In polymer fragments from design objects made of ABS from the 1960s, UV-stabilizers were detected and mapped, and microscopic inclusions of proteinaceous material were identified and mapped for the first time.     

Rapid and simple method for determination of hexabromocyclododecanes and other LC–MS–MS-amenable brominated flame retardants in fish

In this study, a novel analytical approach for simultaneous determination of hexabromocyclododecane isomers (HBCDs), tetrabromobisphenol A (TBBPA), three brominated phenols, and four hydroxylated derivatives of polybrominated diphenyl ethers (OH-PBDEs) was developed and validated for muscle tissue of both lean and fatty fish. The rapid, simple, and high-throughput sample-preparation procedure was based on acetonitrile extraction then purification by dispersive solid-phase extraction (d-SPE) with a combination of C₁₈ and primary–secondary amine (PSA) sorbents. Ultra-high performance liquid chromatography (UHPLC) coupled to tandem mass spectrometry (MS–MS) was used for identification and quantification of the analytes. Method recovery for both matrices ranged from 80 to 115 % with relative standard deviations (RSDs) <13 % for all analytes. Limits of quantification (LOQs) were in the range 0.1–1 μg kg^?1 wet weight. The validated method was used for analysis of brominated compounds in 32 fish and five bivalve samples collected from different European markets within the monitoring survey organized in the framework of the CONffIDENCE project. Of the 12 targeted analytes, only α-HBCD, 2,4-dibromophenol (2,4-DBP), and 2,4,6-tribromophenol (2,4,6-TBP) were quantified in the samples. α-HBCD was found in six fish samples (herring and mackerel) in the range of 0.8–2.5 μg kg^?1 wet weight. 2,4-DBP and 2,4,6-TBP were found in three blue mussel samples in the range of 19.6–43.5 and 2.3–7.5 μg kg^?1 wet weight, respectively.     

A Generalizable and Noncovalent Strategy for Interfacing Aptamers with a Microelectrode for the Selective Sensing of Neurotransmitters In Vivo

The selective sensing of neurochemicals is essential for understanding the chemical basis of brain function and pathology. Interfacing the excellent recognition features of aptamers with in vivo compatible carbon fiber microelectrode (CFE)-based electroanalytical systems offers a plausible means to achieve this end. However, this is challenging in terms of coupling chemistry, stability, and versatility. Here, we present a new interfacial functionalization strategy based on the assembly of aptamer cholesterol amphiphiles (aptCAs) on the alkyl chain-functionalized CFE. The noncovalent cholesterol-alkyl chain interactions effectively immobilize aptamers onto the CFE surface, allowing the generation of a highly selective system for probing neurochemical dynamics in living systems and opening up a vast array of new opportunities for designing in vivo sensors for exploring brain chemistry.     

Field performance test of PASS,an instrument for the rapid assay of plutonium and other γ-ray emitting radionuclides

A field performance test was conducted at the INEL with the mobile Rapid Transuranic Monitoring Laboratory (RTML) that was developed for the analysis of samples from sites or facilities potentially contaminated with plutonium, other actinides, and -ray emitting activation and fission-product radionuclides. The performance test and results are described for the Photon Analysis Spectrometer System (PASS), one of three RTML assay systems. This system consists of a thin-window, n-type Ge spectrometer, that automatically analyzes soil, smear, and air particulate-filter samples for actinides emitting L x rays, and for activation and fission products that emit rays. The measurements were blind and performed with 11-g soil samples gathered from the Cold Test Pit and with spiked samples containing known mixtures of²³⁹Pu,²⁴¹Am⁶⁰Co, and¹³⁷Cs. In the spiked samples the plutonium activity concentrations ranged from 75 to 500 pCi/g while the other radionuclides ranged from 10 to 130 pCi/g. Lower limits of detection (LLDs) were verified to be 1, 5, 5, and 40 pCi/g for²⁴¹Am,⁶⁰Co,¹³⁷Cs, and²³⁹Pu, respectively. Results from the performance test are presented.