The structure in solution and conformational stability of the hemocyanin from the Chilean gastropod mollusk Concholepas concholepas (CCH) and its structural subunits, CCH-A and CCH-B, were studied using fluorescence spectroscopy and differential scanning calorimetry (DSC). The fluorescence properties of the oxygenated and apo-form (copper-deprived) of the didecamer and its subunits were characterized. Besides tryptophan residues buried in the hydrophobic interior of the protein molecule also exposed fluorophores determine the fluorescence emission of the oxy- and apo-forms of the investigated hemocyanins. The copper-dioxygen system at the binuclear active site quenches the tryptophan emission of the oxy-forms of CCH and its subunits. The removal of this system increases the fluorescence quantum yield and causes structural rearrangement of the microenvironment of the emitting tryptophan residues in the respective apo-forms. Time-resolved fluorescence measurements show that the oxygenated and copper-deprived forms of the CCH and its subunits exist in different conformations. The thermal denaturation of the hemocyanin is an irreversible process, under kinetic control. A successive annealing procedure was applied to obtain the experimental deconvolution of the irreversible thermal transitions. Arrhenius equation parameter for the two-state irreversible model of the thermal denaturation of oxy-CCH at pH 7.2 was estimated. Both factors, oligomerization and the copper-dioxygen system at the active site, are important for stabilizing the structure of the hemocyanin molecule.
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Dalton Trans
January 2025
Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UK.
Hexaanionic cyclophosphazenate ligands [(RN)PN] provide versatile platforms for the assembly of multinuclear metal arrays due to their multiple coordination sites and highly flexible ligand core structure. This work investigates the impact of incrementally increasing the steric demand of the ligand periphery on the coordination behavior of ethylzinc arrays. It shows that the increased congestion around the ligand sites is alleviated by progressive condensation with the elimination of diethylzinc.
View Article and Find Full Text PDFNat Struct Mol Biol
January 2025
Laboratory of Molecular Biophysics, The Rockefeller University, New York, NY, USA.
Following transcript release during intrinsic termination, Escherichia coli RNA polymerase (RNAP) often remains associated with DNA in a post-termination complex (PTC). RNAPs in PTCs are removed from the DNA by the SWI2/SNF2 adenosine triphosphatase (ATPase) RapA. Here we determined PTC structures on negatively supercoiled DNA and with RapA engaged to dislodge the PTC.
View Article and Find Full Text PDFNat Commun
January 2025
Department of Medicinal Chemistry, University of Kansas, Lawrence, USA.
One of the hallmarks of RNA viruses is highly structured untranslated regions (UTRs) which are often essential for viral replication, transcription, or translation. In this report, we discovered a series of coumarin derivatives that bind to a four-way RNA helix called SL5 in the 5' UTR of the SARS-CoV-2 RNA genome. To locate the binding site, we developed a sequencing-based method namely cgSHAPE-seq, in which an acylating probe was directed to crosslink with the 2'-OH group of ribose at the binding site to create read-through mutations during reverse transcription.
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January 2025
State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Food Nutrition and Safety, Ministry of Education, College of Food Science and Engineering, Tianjin University of Science & Technology, No. 9, No. 13 Ave., TEDA, Tianjin 300457, China. Electronic address:
There is an urgent need for stable, plant-based Pickering foams to address the growing consumer demand for sustainable, low-calorie, aerated sweet foods. This study employed a cold plasma-assisted deamidation and glycosylation (CPDG) approach to promote hydrophilic reassembly of zein, resulting in the formation of sugar derivative-zein conjugates. This was accomplished by coupling deamidated zein with polyhydroxy sugars including sucralose (Suc), maltitol (Mal), mannitol (Man), and stevioside (Ste).
View Article and Find Full Text PDFFood Res Int
January 2025
State Key Laboratory of Food Science and Resources, National Engineering Research Center of Cereal Fermentation and Food Biomanufacturing, School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu 214122, China; Guangdong Engineering Research Center of High-Value Utilization and Equipment Development of Marine Biological Resources, Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, Guangdong 511458, China; Jiangnan University (Shaoxing) Industrial Technology Research Institute, Shaoxing, Zhejiang 31200, China; National Engineering Research Center of Huangjiu, Zhejiang Guyuelongshan Shaoxing Wine CO., LTD, Shaoxing 646000, Zhejiang, China. Electronic address:
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