We report on the detailed analysis of chemical modifications and structural changes in the cellulose and lignin of
Populus tremula (a hardwood) and
Buxus sempervirens (a softwood), as a result of ...photodegradation in a Xenon test chamber. The results obtained by means of FTIR spectroscopy indicate that lignin is the most sensitive component to the degradation process for both woods examined. On a structural level, the virtual elimination of the amorphous cellulose was observed for both types of wood. The crystallised cellulose I component, which accounts for the whole crystalline phase, undergoes minor structural changes, this effect being more important in the case of
Populus tremula that was less degraded than
Buxus Sempervirens.
•The synthesis of a basic solid catalytic material with strong basic sites is described.•The catalyst is prepared by a simple and low-cost method using biomass waste as the starting material.•The ...catalytic material is quite promising for being used as heterogeneous catalysts.
The synthesis procedure of activated carbons with basic properties is optimized in order to prepare a basic solid with a high number of strong basic active sites on the surface of the carbon material. The basic solid is obtained from biomass waste (olive stone) and present appropriate porous structure for being used as heterogeneous catalyst. The acid/basic properties of the surface of the carbons are studied by pH titrations. These carbon materials are used for the isomerization of lactose to lactulose, which finds many applications in both pharmaceutical and food industries. This reaction is a route for revalorization of whey (which contains lactose). The results show that these carbon materials are quite promising for being used as heterogeneous catalysts for this reaction, avoiding the use of corrosive homogeneous catalysts and revalorizing two different biomass wastes (olive stone and whey).
G-protein-coupled receptors (GPCR) are a major class of membrane proteins belonging to a continuously growing superfamily. These receptors play a critical role in signal transduction, and are among ...the most important pharmacological drug targets. The first structural model for the GPCR superfamily was the bacterial protein bacteriorhodopsin with its characteristic seven transmembrane (TM) helical architecture. The visual photoreceptor rhodopsin is a better model for GPCR, and the recent elucidation of the crystal structure of bovine rhodopsin has renewed the interest in this receptor as a template for molecular modeling of other GPCR, particularly for the implications in ligand design and drug discovery. In this work different specific structural elements of rhodopsin are reviewed and the role of conserved motifs, like those associated with receptor function, is analyzed. The specific characteristics of the membrane-embedded ligand-binding domain are described. Other aspects, like receptor dimerization or the constitutive activity mechanism, are also outlined. The importance of acquiring knowledge of the active conformation of the receptor by means of both modeling and experimental techniques is also highlighted. In this regard, the model of the activated form of rhodopsin is currently under investigation, and it may provide useful information for pharmaceutical design. Rhodopsin will continue to be a widely used model for GPCR but rhodopsin-based approaches have to be complemented by other theoretical and experimental approaches -while waiting for the crystal structure of other members of the superfamily- if these want to be successfully used for drug discovery.
G protein-coupled receptors (GPCRs) play critical roles in cellular processes and signaling and have been shown to form heteromers with diverge biochemical and/or pharmacological activities that are ...different from those of the corresponding monomers or homomers. However, despite extensive experimental results supporting the formation of GPCR heteromers in heterologous systems, the existence of such receptor heterocomplexes in the brain remains largely unknown, mostly because of the lack of appropriate methodology. Herein, we describe the in situ proximity ligation assay procedure underlining its high selectivity and sensitivity to image GPCR heteromers with confocal microscopy in brain sections. We describe here how the assay is performed and discuss advantages and disadvantages of this method compared with other available techniques.
The rhodopsin mutants P23H and G188R, identified in autosomal dominant retinitis pigmentosa (ADRP), and the site-specific mutants D190A and Δ Y191-Y192 were expressed in COS cells from synthetic ...mutant opsin genes containing these mutations. The proteins expressed from P23H and D190A partially regenerated the rhodopsin chromophore with 11-cis-retinal and were mixtures of the correctly folded (retinal-binding) and misfolded (non-retinal-binding) opsins. The mixtures were separated into pure, correctly folded mutant rhodopsins and misfolded opsins. The proteins expressed from the ADRP mutant G188R and the mutant Δ Y191-Y192 were composed of totally misfolded non-retinal-binding opsins. Far-UV CD spectra showed that the correctly folded mutant rhodopsins had helical content similar to that of the wild-type rhodopsin, whereas the misfolded opsins had helical content 50-70% of the wild type. The near-UV CD spectra of the misfolded mutant proteins lack the characteristic band pattern seen in the wild-type opsin, indicative of a different tertiary structure. Further, whereas the folded mutant rhodopsins were essentially resistant to trypsin digestion, the misfolded opsins were degraded to small fragments under the same conditions. Therefore, the misfolded opsins appear to be less compact in their structures than the correctly folded forms. We suggest that most, if not all, of the point mutations in the intradiscal domain identified in ADRP cause partial or complete misfolding of rhodopsin.
GPR39 is a class A G protein-coupled receptor involved in zinc binding and glucose homeostasis regulation, among other physiological processes. GPR39 was originally thought to be the receptor for ...obestatin peptide but this view has been challenged. However, activation of this receptor by zinc has been clearly established. Recent studies suggest that low GPR39 expression, due to deficient zinc levels, is involved in major depressive disorder. We have previously reported that zinc can alter receptor–receptor interactions and favor specific receptor interactions. In order to unravel the effect of zinc on specific G protein-coupled receptor association processes, we have performed FRET and co-immunopurification studies with GPR39 and 5-HT1A and GalR1 which have been shown to dimerize. Our results suggest that zinc can modulate the formation of specific 5-HT1A-GPR39 and GalR1-5-HT1A-GPR39 heteroreceptor complexes under our experimental conditions.
We have analyzed the differences in signaling between the mono-homomeric receptors 5-HT1A, GalR1 and GPR39 and the heteroreceptor complexes between them Our results show that the GPR39-5-HT1A heterocomplex has additive functionalities when compared to the monomeric–homomeric receptors upon receptor activation. In addition, the heterocomplex including also GalR1 shows a different behavior, upon exposure to the same agonists. Furthermore, these processes appear to be regulated by zinc. These findings provide a rationale for the antidepressive effect widely described for zinc because pro-depressive heterocomplexes are predominant at low zinc concentration levels.
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•GPR39 is able to form heterodimers with 5-HT1A upon co-expression of the two receptors in mammalian cells.•GPR39, 5-HT1A and GalR1 are able to form heterotrimers upon co-expression of the three receptors in mammalian cells.•The different heteromeric forms exhibit different signaling properties compared to their monomeric states.•The balance among the three different forms, 5-HT1A-GalR1, GPR39-5-HT1A-GalR1 and GPR39-5-HT1A would be regulated by zinc.
•GalR1–GalR2 heteroreceptor complexes exist in cellular models and raphe-hippocampal system.•Gal1–15 vs Gal1–29 preferentially activates the GalR1 protomer Gi/o mediated signaling.•Gal1–15 cannot ...activate the GalR2 protomer Gq mediated signaling in the heteromers.•Gal1–29 strongly increases GalR2 Gq mediated signaling in GalR1–GalR2 heteromers and GalR2 homomers.•The dominance of GalR1 vs GalR2 induced by Gal1–15 suggests strong depression like actions.
The three cloned galanin receptors show a higher affinity for galanin than for galanin N-terminal fragments. Galanin fragment (1–15) binding sites were discovered in the rat Central Nervous System, especially in dorsal hippocampus, indicating a relevant role of galanin fragments in central galanin communication. The hypothesis was introduced that these N-terminal galanin fragment preferring sites are formed through the formation of GalR1–GalR2 heteromers which may play a significant role in mediating galanin fragment (1–15) signaling. In HEK293T cells evidence for the existence of GalR1–GalR2 heteroreceptor complexes were obtained with proximity ligation and BRET2 assays. PLA positive blobs representing GalR1–GalR2 heteroreceptor complexes were also observed in the raphe-hippocampal system. In CRE luciferase reporter gene assays, galanin (1–15) was more potent than galanin (1–29) in inhibiting the forskolin-induced increase of luciferase activity in GalR1–GalR2 transfected cells. The inhibition of CREB by 50nM of galanin (1–15) and of galanin (1–29) was fully counteracted by the non-selective galanin antagonist M35 and the selective GalR2 antagonist M871. These results suggested that the orthosteric agonist binding site of GalR1 protomer may have an increased affinity for the galanin (1–15) vs galanin (1–29) which can lead to its demonstrated increase in potency to inhibit CREB vs galanin (1–29). In contrast, in NFAT reporter gene assays galanin (1–29) shows a higher efficacy than galanin (1–15) in increasing Gq/11 mediated signaling over the GalR2 of these heteroreceptor complexes. This disbalance in the signaling of the GalR1–GalR2 heteroreceptor complexes induced by galanin (1–15) may contribute to depression-like actions since GalR1 agonists produce such effects.
Bioscouring of cotton is normally carried out using pectinases having pectate lyase activity. The present study has examined the influence of pectate lyase and hydrolase on the surface of cotton ...fibre. Dye uptake by cotton scoured with polygalacturonase is found to be much lower than that scoured with pectate lyase, Pectate lyase gave better dye exhaustion at 90 °C. The difference in dye exhaustion after scouring with sodium hydroxide, polygalacturonase or pectate lyase, may be due to variation in the amount of surfactant retained by the fibre, as this hinders dye uptake. This was particularly the case with polygalacturonase. Reduced numbers of free carboxy groups on the fibre surface could indicate lower pectin content. On the other hand it could, however, be due to the esterification of carboxy groups in the pectin by hydroxy groups in the surfactant.
An analysis of variance has been applied to study the individual effects and the interaction between the process parameters, temperature, pH, and surfactant concentration, in the bioscouring of ...cotton fibers with an acid pectinase. This study indicates that increasing the temperature does not increase the total percentage of bioscouring but accelerates the rate of the process. The pH and surfactant seem to be determinant for the optimal enzyme performance under the studied conditions.
The enzyme–substrate ratio has been analyzed and a kinetic study at different enzyme concentrations has been carried out.
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