The formation of self-assembled monolayers (SAMs) of representative thiocarbohydrate derivatives onto a gold surface has been investigated to build an artificial carbohydrate scaffold to mimic non-bonded molecular recognition phenomena. Three types of carbohydrate SAMs were formulated from (i) 1-β-Dthioglucose (1), (ii) 1-β-D-thioglucose tetraacetate (2), and (iii) 2-mercaptoethyl R-D-mannopyranoside (3). Subsequently, each SAM was spectroscopically characterized by reflection-absorption infrared spectroscopy (RAIRS). Deprotection of the acylated carbohydrate SAM was achieved in situ, indicating that chemical transformation may be performed without disruption of the sulfursgold bond. With the mannose derivative, in which the carbohydrate moiety was separated from the gold surface by the spacer unit sOCH2CH2SH, it was possible to demonstrate that such a carbohydrate SAM was able to interact selectively with a specific carbohydrate binding protein, i.e., concanavalin A (Con A). Exposure of the mannose derived SAM to a solution of Con A led to a specific binding interaction as measured by RAIRS and surface plasmon resonance (SPR). In contrast, on exposure of the mannose SAM to the L-fucose-specific lectin tetragonolobus purpureas, no such binding was observed. These results suggest that highly ordered SAMs of specifically designed carbohydrate derivatives can be formulated to mimic natural cell surface structures and used to study selective molecular recognition interactions.
Aequorin, the bioluminescent protein found in the jellyfish Aequorea sp., has been immobilized in a porous sol-gel glass environment. The luminescence from this protein is specifically triggered by the presence of calcium ions, thus offering exciting possibilities for the development of an optical biosensor for this cationic species. The luminescence emission spectrum has been measured from the aequorin protein after interaction with calcium ions. The intensity of the luminescence, measured at the peak maximum of 470 nm, for the encapsulated protein has been calibrated against calcium ion concentration. The characterization of the protein within the sol-gel matrix has been reported together with biosensing experiments using human sera and milk samples. The results suggest that the sol-gel encapsulated aequorin protein offers potential as a one shot bioluminescence based biosensor for the determination of calcium ions in such complex matrices.
The metalloprotein cytochrome c' was extracted and purified from the bacterium Paracoccus denitrificans in order to develop a specific biosensing system for nitric oxide (NO). The metalloprotein was encapsulated in a porous silicate sol-gel glass to enable spectroscopic changes in the haem centre as a function of NO ligation to be quantified using absorption measurements. Spectroscopic evidence suggested that, between 2 and 4 d after encapsulation, the cytochrome c' protein changed conformation in the locality of the haem moiety, possibly from a five to a six coordinate haem centre. Such conformational changes were also observed when the cytochrome c' was stored in solution, although over a 2-3 month period. The conformational changes occurring in the protein altered the spectral characteristics of the reduced, oxidised and nitrosyl complex of the cytochrome c' and appear to change the binding affinity of the protein towards NO. However, the encapsulated (reconformed) cytochrome c' was shown to retain its selectivity towards NO with good reproducibility (seven consecutive measurements of NO produced an intensity value with a relative standard deviation of 0.28%). An NO calibration curve, using the in situ release of NO from the donor diethylamine NONOate, was obtained for the encapsulated cytochrome c' with an approximate working range of 10-400 mumol l-1.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.