scholarly journals SYNTHESIS AND CHARACTERIZATION OF HYDROXYPROPYL CELLULOSE-CYSTEAMINE CONJUGATE AS A NOVEL CATIONIC THIOMER WITH LIPOPHILIC PROPERTIES

2019 ◽  
Vol 11 (1) ◽  
pp. 222 ◽  
Author(s):  
Deni Rahmat ◽  
Fikry A. R. Rahman ◽  
Liliek Nurhidayati ◽  
Dian Ratih Laksmitawati
Keyword(s):  
Reductive Amination ◽  
Ph Value ◽  
Thiol Group ◽  
Hydroxypropyl Cellulose ◽  
Scanning Calorimetry ◽  
Swelling Behaviour ◽  
Chemically Modified ◽  
Time Period ◽  
Free Thiol Group

Objective: Thiomers have been known as polymer with mucoadhesive properties. The aim of this study was to synthesize the mucoadhesive potential of hydroxypropyl cellulose-cysteamine conjugate (HPC-cysteamine).Methods: The parent polymer HPC was chemically modified by introducing sulphydryl bearing compound using reductive amination. HPC-cysteamine conjugates were prepared at reaction pH value of 5. The reaction was stabilized by the addition of cyanoborohydride. Afterwards, the conjugate was evaluated for optimum free thiol group, swelling behavior, viscosity and mucoadhesive properties.Results: The conjugates showed maximum thiol incorporation on HPC of 1063.03±64.27 µmol/g. The disulphide groups content was 278.71±32.14 μmol/g. Mucoadhesion studies revealed that mucoadhesion of HPC-cysteamine demonstrated 26 h. The swelling behaviour of HPC-cysteamine tablets increased within the time period of study. The viscosity of HPC-cysteamine was higher than that of unmodified HPC. The thermal profile of HPC-cysteamine and unmodified HPC analyzed by differential scanning calorimetry (DSC) displayed a different enthalpy (ΔH) value.Conclusion: HPC-cysteamine conjugate renders better properties which might be more beneficial for drug delivery system compared to unmodified HPC. 

scholarly journals Further characterization of the covalent linking reaction of α2-macroglobulin

1981 ◽  
Vol 195 (2) ◽  
pp. 453-461 ◽  
Author(s):  
G S Salvesen ◽  
C A Sayers ◽  
A J Barrett
Keyword(s):  
Steric Hindrance ◽  
Peptide Mapping ◽  
Thiol Group ◽  
Molar Ratio ◽  
Reactive Site ◽  
Reactive Group ◽  
Α2 Macroglobulin ◽  
Free Thiol Group ◽  
Covalently Linked

It is shown that non-proteolytic proteins can become covalently linked to alpha 2M (alpha 2-macroglobulin) during its reaction with proteinases, and that this probably occurs by the mechanism that leads to the covalent linking of proteinases described previously [Salvesen & Barrett (1980) Biochem. J. 187, 695-701]. The covalent linking of trypsin was at least partly dependent on the presence of unblocked lysine side chains on the protein. The covalent linking of proteinases was inhibited by nucleophiles of low Mr, and these compounds were themselves linked to alpha 2M in a molar ratio approaching one per quarter subunit. Peptide “mapping” indicated that the site of proteinase-mediated incorporation of the amines was the same as that at which methylamine is incorporated in the absence of a proteinase. The nucleophile-reactive site revealed in alpha 2M after reaction with a proteinase was shown to decay with a t1/2 of 112 s, at pH 7.5. After the reaction with a proteinase or with methylamine, a free thiol group was detectable on each subunit of alpha 2M. We propose that the site for incorporation of methylamine in each subunit is a thiol ester, which in S-alpha 2M (the electrophoretically “slow” form) is sterically shielded from reaction with large nucleophiles, but is revealed as a highly reactive group, free from steric hindrance, after the proteolytic cleavage. We have designated the activated species of the molecule “lpha 2M”.

scholarly journals Halogenation of β-estradiol by a rationally designed mesoporous biocatalyst based on chloroperoxidase

Biocatalysis ◽  
2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Karina Salcedo ◽  
Eduardo Torres-Ramírez ◽  
Iliana Haces ◽  
Marcela Ayala
Keyword(s):  
Specific Activity ◽  
Thiol Group ◽  
Covalent Immobilization ◽  
Amino Acid Residues ◽  
Caldariomyces Fumago ◽  
Chemically Modified ◽  
Diazonium Ions ◽  
Free Thiol Group ◽  
Reactive Groups ◽  
Aromatic And Aliphatic Amines

AbstractChloroperoxidase from Caldariomyces fumago was immobilized in Eupergit® C, a commercial mesoporous acrylic-based material. Due to low stability of the enzyme under neutral and basic pH, the usual covalent immobilization procedures cannot be applied to this enzyme. Several strategies were followed in order to achieve a stable interaction between the protein and the support. The support was efficiently functionalized with different reactive groups such as aromatic and aliphatic amines, glutaraldehyde, diazonium ions, and maleimide moieties; solvent-exposed amino acid residues in chloroperoxidase were identified or created through chemical modification, so that they were reactive under conditions where the enzyme is stable. Enzyme load and retained activity were monitored, obtaining biocatalysts with specific activity ranging from 200 to 25,000 U/g. The highest load and activity was obtained from the immobilization of a chemically-modified CPO preparation bearing a solvent-exposed free thiol group. This biocatalyst efficiently catalyzed the transformation of β-estradiol, an endocrine disruptor.

Preparation and Characterization of a High-Efficient Potassium Adsorbent H8Nb22O59·8H2O

2014 ◽  
Vol 1079-1080 ◽  
pp. 46-49
Author(s):  
Chang Wang ◽  
Peng Fei Cao ◽  
Xiang Long Zhang
Keyword(s):  
Ion Exchange ◽  
Calcination Temperature ◽  
Ph Value ◽  
Distribution Coefficients ◽  
Adsorptive Capacity ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
High Efficient ◽  
Separation Factors

The adsorbent of H8Nb22O59·8H2O and the precursor of Rb8Nb22O59 were characterized by X-ray diffraction (XRD), Thermogravimetric and differential scanning calorimetry (TG-DSC), and scanning electron microscope (SEM). The ion-exchange properties of H8Nb22O59·8H2O for Na+ and K+ were also investigated, including the saturation adsorptive capacity, distribution coefficients and separation factor. The results show that the crystallinity of Rb8Nb22O59 was affected by the calcination temperature. The structure of Rb8Nb22O59 was not changed when Rb+ was extracted from Rb8Nb22O59, indicating that this process was topotactical. The calcination temperature and pH value had a significant influence on the ion-exchange capacities of H8Nb22O59·8H2O for Na+ and K+. Specifically, the uptake amouts of Na+ and K+ by H8Nb22O59·8H2O increased with the calcination temperature, while the distribution coefficients of Na+ and K+ for H8Nb22O59·8H2O increased with the pH value. Moreover, the separation factors for K+ was larger than that for Na+ and it increased with the increase of calcination temperature. Overall, the improvement of the crystallinity of H8Nb22O59·8H2O was beneficial to its selectivity for K+.

scholarly journals Chemical Modification and Characterization of Yeast Cells for Extraction of Metal Ion in Water Sample

2014 ◽  
Vol 10 (8) ◽  
pp. 3037-3041
Author(s):  
Homayon Ahmad Panahi
Keyword(s):  
Water Sample ◽  
Metal Ion ◽  
Sea Water ◽  
Ph Value ◽  
Yeast Cells ◽  
Nickel Ions ◽  
Cibacron Blue ◽  
Chemically Modified ◽  
Equilibrium Data

A novel biosorbent is prepared by coupling a cibacron blue to yeast cells. The chemically modified yeast cells with mentioned ligand has been characterized by Fourier transform infrared spectroscopy and elemental analysis and applied for the preconcentration and extraction of trace Ni(II) from water samples. The optimum pH value for sorption of the nickel ions was 8. The sorption capacity of yeast cells- cibacron blue is 12.2 mg. g−1. A recovery of 91.4% was obtained for Ni(II) when eluted with 0.5 M HCl/HNO3 (3:1). The equilibrium data of Ni(II) adsorption on yeast cells- cibacron blue was analyzed using Langmuir model. The method was applied for Ni(II) determination in sea water sample.

Light-cured dental composites characterization by Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 428-429
Author(s):  
B. M. Culbertson ◽  
M. L. Devinev ◽  
E. C. Kao
Keyword(s):  
Electron Microscopy ◽  
Mechanical Analysis ◽  
Service Performance ◽  
Dental Composite ◽  
Dental Composites ◽  
Neat Resin ◽  
Scanning Calorimetry ◽  
Research Meeting ◽  
Formulation Variables

The service performance of current dental composite materials, such as anterior and posterior restoratives and/or veneer cements, needs to be improved. As part of a comprehensive effort to find ways to improve such materials, we have launched a broad spectrum study of the physicochemical and mechanical properties of photopolymerizable or visible light cured (VLC) dental composites. The commercially available VLC materials being studied are shown in Table 1. A generic or neat resin VLC system is also being characterized by SEM and TEM, to more fully understand formulation variables and their effects on properties.At a recent dental research meeting, we reported on the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) characterization of the materials in Table 1. It was shown by DSC and DMA that the materials are substantially undercured by commonly used VLC techniques. Post curing in an oral cavity or a dry environment at 37 to 50°C for 7 or more hours substantially enhances the cure of the materials.

Glibenclamide-Nicotinamide Cocrystals Synthesized by The Solvent Evaporation Method to Enhance Solubility and Dissolution Rate of Glibenclamide

2019 ◽  
Vol 9 (01) ◽  
pp. 21-26
Author(s):  
Arif Budiman ◽  
Ayu Apriliani ◽  
Tazyinul Qoriah ◽  
Sandra Megantara
Keyword(s):  
Solvent Evaporation ◽  
Physical Mixture ◽  
Dissolution Profile ◽  
Solvent Evaporation Method ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Evaporation Method ◽  
Dissolution Properties ◽  
Mixture Characterization

Purpose: To develop glibenclamide-nicotinamide cocrystals with the solvent evaporation method and evaluate their solubility and dissolution properties. Methods: Cocrystals of glibenclamide-nicotinamide (1:2) were prepared with the solvent evaporation method. The prediction of interactive cocrystals was observed using in silico method. The solubility and dissolution were performed as evaluation of cocrystals. The cocrystals also were characterized by differential scanning calorimetry (DSC), infrared spectrophotometry, and powder X-ray diffraction (PXRD). Result: The solubility and dissolution profile of glibenclamide-nicotinamide cocrystal (1:2) increased significantly compared to pure glibenclamide as well as its physical mixture. Characterization of cocrystal glibenclamide-nicotinamide (1:2) including infrared Fourier transform, DSC, and PXRD, indicated the formation of a new solid crystal phase differing from glibenclamide and nicotinamide. Conclusion: The confirmation of cocrystal glibenclamide-nicotinamide (1:2) indicated the formation of new solid crystalline phases that differ from pure glibenclamide and its physical mixture

Studies on the Preparation, Characterization and Solubility of -Cyclodextrin-Roxythromycin Inclusion Complexes

2009 ◽  
Vol 2 (2) ◽  
pp. 523-530
Author(s):  
D. Nagasamy Venkatesh ◽  
S. Karthick ◽  
M. Umesh ◽  
G. Vivek ◽  
R.M. Valliappan ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Inclusion Complexes ◽  
Phase Solubility ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Ir Studies ◽  
Poorly Soluble ◽  
Poorly Soluble Drug

Roxythromycin/ β-cyclodextrin (Roxy/ β-CD) dispersions were prepared with a view to study the influence of β-CD on the solubility and dissolution rate of this poorly soluble drug. Phase-solubility profile indicated that the solubility of roxythromycin was significantly increased in the presence of β-cyclodextrin and was classified as AL-type, indicating the 1:1 stoichiometric inclusion complexes. Physical characterization of the prepared systems was carried out by differential scanning calorimetry (DSC), X-ray diffraction studies (XRD) and IR studies. Solid state characterization of the drug β-CD binary system using XRD, FTIR and DSC revealed distinct loss of drug crystallinity in the formulation, ostensibly accounting for enhancement of dissolution rate.

AFM and SEM Characterization of Chemically Modified Electrodes Based on 5-[(azulen-1-yl) methylene]-2-thioxothiazolidin-4-one

2018 ◽  
Vol 68 (12) ◽  
pp. 2799-2803
Author(s):  
Maria Daniela Pop ◽  
Oana Brincoveanu ◽  
Mihaela Cristea ◽  
George Octavian Buica ◽  
Marius Enachescu ◽  
...  
Keyword(s):  
Glassy Carbon ◽  
Roughness Parameter ◽  
Modified Electrodes ◽  
Chemically Modified Electrodes ◽  
Adhesion Properties ◽  
Chemically Modified ◽  
Controlled Potential ◽  
Constant Potential ◽  
Metal Ions Detection

Preparation and microscopy characterization of polymer modified glassy carbon electrodes based on (5-[(azulen-1-yl) methylene]-2-thioxothiazolidin-4-one (L) were reported. Atomic Force Microscopy was used to investigate the morphological and mechanical properties of the deposited polyL films onto glassy carbon. The topography images of the analyzed samples exhibited the presence of some columnar shape features onto the layer surfaces. The surface roughness of the layers deposited at constant charge calculated from topography images, increased with the more positive applied potential for controlled potential electrolysis. At different charges, the roughness parameter showed the same behavior for the layers obtained applying a constant potential without having a noticeable influence on the adhesion properties on the substrate. Analysis using scanning electron microscopy shows a relatively uniform surface arrangement of the polymer and the presence of some clusters which are disturbing the planarity. PolyL chemically modified electrodes have been used for heavy metal ions detection with best results for lead.

Thermal Behaviour of Candesartan Active substance and in pharmaceutical compounds

2017 ◽  
Vol 68 (8) ◽  
pp. 1895-1902
Author(s):  
Ioana Cristina Tita ◽  
Eleonora Marian ◽  
Bogdan Tita ◽  
Claudia Crina Toma ◽  
Laura Vicas
Keyword(s):  
Thermal Behaviour ◽  
Active Substance ◽  
Pharmaceutical Research ◽  
Pharmaceutical Product ◽  
Nitrogen Atmosphere ◽  
Pure Substance ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Ft Ir

Thermal analysis is one of the most frequently used instrumental techniques in the pharmaceutical research, for the thermal characterization of different materials from solids to semi-solids, which are of pharmaceutical relevance. In this paper, simultaneous thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) were used for characterization of the thermal behaviour of candesartan cilexetil � active substance (C-AS) under dynamic nitrogen atmosphere and nonisothermal conditions, in comparison with pharmaceutical product containing the corresponding active substance. It was observed that the commercial samples showed a different thermal profile than the standard sample, caused by the presence of excipients in the pharmaceutical product and to possible interaction of these with the active substance. The Fourier transformed infrared spectroscopy (FT-IR) and X-ray powder diffraction (XRPD) were used as complementary techniques adequately implement and assist in interpretation of the thermal results. The main conclusion of this comparative study was that the TG/DTG and DSC curves, together with the FT-IR spectra, respectively X-ray difractograms constitute believe data for the discrimination between the pure substance and pharmaceutical forms.

Gelatin and Glycerine-Based Bioadhesive Vaginal Hydrogel

2020 ◽  
Vol 17 (4) ◽  
pp. 303-311
Author(s):  
Roberta Cassano ◽  
Federica Curcio ◽  
Delia Mandracchia ◽  
Adriana Trapani ◽  
Sonia Trombino
Keyword(s):  
Differential Scanning Calorimetry ◽  
Inflammatory Process ◽  
Vaginal Mucosa ◽  
Vaginal Infection ◽  
Scanning Calorimetry ◽  
Time Intervals ◽  
Site Specific ◽  
Release Studies ◽  
Hiv Seropositive

Aim: The work’s aim was the preparation and characterization of a hydrogel based on gelatin and glycerine, useful for site-specific release of benzydamine, an anti-inflammatory drug, able to attenuate the inflammatory process typical of the vaginal infection. Objective: The obtained hydrogel has been characterized by Electronic Scanning Microscopy (SEM) and Differential Scanning Calorimetry (DSC). In addition, due to the precursor properties, the hydrogel exhibits a relevant mucoadhesive activity. Methods: The swelling degree was evaluated at two different pHs and at defined time intervals. In particular, phosphate buffers were used at pH 6.6, in order to mimic the typical conditions of infectious diseases at the vaginal level, particularly for HIV-seropositive pregnant women, and pH 4.6, to simulate the physiological environment. Results: The obtained results revealed that the hydrogel swells up well at both pHs. Conclusion: Release studies conducted at both pathological and physiological pHs have shown that benzydamine is released at the level of the vaginal mucosa in a slow and gradual manner. These data support the hypothesis of the hydrogel use for the site-specific release of benzydamine in the vaginal mucosa.

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