Papers by Keyword: Thiols

Abstract: Thiols play key roles in biological systems. They are important parts of many organisms proteins and small molecules, and have an important role in cellular antioxidant systems. In recent years, fluorescent methods for detecting the mercapto compounds have developed rapidly, based on its apparent advantages in sensitivity, specificity and nondestructive imaging. Therefore, the quantitative detection of mercapto biomolecules are very important in biochemical and clinical chemistry. In this review,we summarized the fluorescent probes for thiols according to their unique mechanisms between fluorescent probes and thiols.

Abstract: Thiosulfinates are a major compound found in most allium plant. Garlic, an allium species shows its potential to inhibit microbial and enzyme activity. The usage of garlic is widely known especially in the agriculture field. Thiosulfinates are formed by reaction of alliinase enzyme from their respective S-alk(en)yl cysteine sulfoxide after the crushing process of the garlic cloves. The stability of the garlic extract has been tested at variations of temperatures and pH values at different incubation time in terms of concentration (mM). After consecutive 4 hour incubation, thiols show higher concentration at temperature 30-35°C. The minimum concentration shows 22% reduction from the original thiols reading. Meanwhile, pH values of 2 (acidic) at 35°C gives higher thiols concentration compared to other conditions.

Abstract: Double conjugate addition of thiols with dienones was catalyzed by amino acids at room temperature in methanol, to afford the corresponding addition product in good to excellent yields.

Abstract: In the presence of L-proline, an efficient and direct double aza-Michael addition of thiols with dienones has been realized, affording functionalized sulfur-containing products in excellent yields (94%-97%).

Abstract: Gadolinium complex of 2-aminothiophenol conjugated DTPA (DTPA=diethylenetriamine N,N,N',N",N" pentacetic acid) bis (amide) has been synthesized and characterized by various analytical techniques such as elemental analysis (EA), NMR, FAB-MS, IR, UV etc. This thiolated GdL (where L is a conjugate of DTPA and 2-aminothiophenol) has been anchored on the gold nanoparticles surfaces through thiols functionalites. These gold nanoparticles (AuNPs) have been synthesized by the reduction of gold tetrachloride (HAuCl₄) using sodium citrate as reducing agent. The surface functionalization has been performed by the replacement of citrate coat on the gold nanoparticle surface with thiolated Gd-chelate, Au@GdL. The Au@GdL has been analyzed by XRD, transmission electron microscope (HRTEM), UV, ICP-MS etc. The average size of nanoparticles is about 22 nm with a uniform spherical shape. A very high number of GdL has been loaded on nanoparticle surface reaching up to 7.9x10³ of Gd (III)- chelates per nanoparticle and they demonstrate very high r₁ relaxivity and the r₁ relaxivity per [G is much higher than the Gd (III)-chelate alone. The bimodality has also been tested using in-vitro x-ray computed tomography (x-ray CT). These nanoparticles (GNPs) are very stable and homogeneously dispersed in aqueous solution.

Abstract: Cysteine and homocysteine are the biological thiols which have an important function in various biochemical processes in our body. Alterations in their level lead to various abnormalities. Therefore, we fabricated a miniaturized platform for capillary electrophoresis that could separate and detect these amino thiols electrochemically. The device was fabricated using conventional photolithography technique on the glass substrate. The microchannel was molded in polydimethylsiloxane with gold electrodes deposited on glass for separation and detection. Based on the amperometric detection, we could detect cysteine in 93 sec while homocysteine was detected in 111 sec.

Abstract: The formation of self-assembled monolayers (SAMs) by specific organic molecules with appropriate anchor groups on semiconductor surfaces may be used to probe the chemical state and quality of the surface or to achieve surface passivation. Molecules with thiol anchor groups are able to bond to hydrogen-terminated germanium surfaces (Ge-S bond). We have prepared SAMs of alkylthiols with different head groups on germanium. Since the surface preparation of germanium is neither well understood nor developed, the controlled preparation of an oxide-free completely H-terminated surface which is a prerequisite for SAM formation of alkylthiols turned out to be a major challenge. Several approaches have been studied. The characterization of the germanium surface prior to and after SAMs formation has been performed by AFM, XPS, Synchrotron-TXRF and -NEXAFS.

Abstract: In this paper, a new method based on molecular self-assembly on carbon fiber surface was proposed for the improvement of interfacial properties between fiber and epoxy matrix in a composite system. In order to obtain the controlled interphase, the surface of carbon fibers was first metallized by electroless Ag plating, then was reacted with terminally functionized alkanethiols or aromatic thiols to form Ag-thiolate thin films, which further reacted with epoxy resin to generate a strong adhesion interface. The composition, structure and the morphology of the modified carbon fiber surface were examined by X-ray photoelectron spectroscopy (XPS), surface-enhanced Raman scattering (SERS) and atomic force microscope (AFM), respectively. The results showed that these self-assembly molecules were chemisorbed onto the carbon fiber surface coated with silver via the strong S-Ag bond. In addition, these thiol molecules act as coupling agents between the epoxy matrix and carbon fiber through active functional end-groups, such as –OH, -NH2. The interfacial shear strength (IFSS) of the microcomposites after introduced the controlled interphase using the microbond testing was improved.