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      ANS fluorescence: Potential to discriminate hydrophobic sites of proteins in solid states


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          In the current study, ANS fluorescence was established as a powerful tool to study proteins in solid-state. Silk fibroin from Bombyx mori cocoons was used as a paradigm protein. ANS incorporated into the films of silk fibroin exhibits fluorescence with two-lifetime components that can be assigned to the patches and/or cavities with distinct hydrophobicities. Decay associated spectra (DAS) of ANS fluorescence from both sites could be fit to the single log-normal component indicating their homogeneity. ANS binding sites in the protein film are specific and could be saturated by ANS titration. ANS located in the binding site that exhibits the long-lifetime fluorescence is not accessible to the water molecules and its DAS stays homogeneously broadened upon hydration of the protein film. In contrast, ANS from the sites demonstrating the short-lifetime fluorescence is accessible to water molecules. In the hydrated films, solvent-induced fluctuations produce an ensemble of binding sites with similar characters. Therefore, upon hydration, the short-lifetime DAS becomes significantly red-shifted and inhomogeneously broadened. The similar spectral features have previously been observed for ANS complexed with globular proteins in solution. The data reveal the origin of the short-lifetime fluorescence component of ANS bound to the globular proteins in aqueous solution. Findings from this study indicate that ANS is applicable to characterize dehydrated as well as hydrated protein aggregates, amyloids relevant to amyloid diseases, such as Alzheimer's, Parkinson, and prion diseases.

          Graphical abstract


          • ANS has the potential to characterize proteins in solid states.

          • ANS fluorescence in protein films reveals the hydrophobic sites with distinct properties.

          • Short lifetime DAS of ANS in hydrated protein films is similar to that of ANS-protein complexes in solution.

          • ANS is applicable to characterize protein aggregates relevant to the Alzheimer's, Parkinson, and prion diseases.

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          Extrinsic Fluorescent Dyes as Tools for Protein Characterization

          Noncovalent, extrinsic fluorescent dyes are applied in various fields of protein analysis, e.g. to characterize folding intermediates, measure surface hydrophobicity, and detect aggregation or fibrillation. The main underlying mechanisms, which explain the fluorescence properties of many extrinsic dyes, are solvent relaxation processes and (twisted) intramolecular charge transfer reactions, which are affected by the environment and by interactions of the dyes with proteins. In recent time, the use of extrinsic fluorescent dyes such as ANS, Bis-ANS, Nile Red, Thioflavin T and others has increased, because of their versatility, sensitivity and suitability for high-throughput screening. The intention of this review is to give an overview of available extrinsic dyes, explain their spectral properties, and show illustrative examples of their various applications in protein characterization.
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            Silkworm silk-based materials and devices generated using bio-nanotechnology

            Silks are natural fibrous protein polymers that are spun by silkworms and spiders. This tutorial review summarizes and highlights recent advances in the use of silkworm silk-based materials in bio-nanotechnology. Silks are natural fibrous protein polymers that are spun by silkworms and spiders. Among silk variants, there has been increasing interest devoted to the silkworm silk of B. mori , due to its availability in large quantities along with its unique material properties. Silk fibroin can be extracted from the cocoons of the B. mori silkworm and combined synergistically with other biomaterials to form biopolymer composites. With the development of recombinant DNA technology, silks can also be rationally designed and synthesized via genetic control. Silk proteins can be processed in aqueous environments into various material formats including films, sponges, electrospun mats and hydrogels. The versatility and sustainability of silk-based materials provides an impressive toolbox for tailoring materials to meet specific applications via eco-friendly approaches. Historically, silkworm silk has been used by the textile industry for thousands of years due to its excellent physical properties, such as lightweight, high mechanical strength, flexibility, and luster. Recently, due to these properties, along with its biocompatibility, biodegradability and non-immunogenicity, silkworm silk has become a candidate for biomedical utility. Further, the FDA has approved silk medical devices for sutures and as a support structure during reconstructive surgery. With increasing needs for implantable and degradable devices, silkworm silk has attracted interest for electronics, photonics for implantable yet degradable medical devices, along with a broader range of utility in different device applications. This Tutorial review summarizes and highlights recent advances in the use of silk-based materials in bio-nanotechnology, with a focus on the fabrication and functionalization methods for in vitro and in vivo applications in the field of tissue engineering, degradable devices and controlled release systems.
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              Excited State Electron and Proton Transfers


                Author and article information

                Biochem Biophys Rep
                Biochem Biophys Rep
                Biochemistry and Biophysics Reports
                03 November 2020
                December 2020
                03 November 2020
                : 24
                [1]Laboratory of Structure, Dynamics and Functions of Biomolecules, Institute of Biophysics of ANAS, 117 Z. Khalilov, Baku, AZ1171, Azerbaijan
                Author notes
                S2405-5808(20)30153-9 100843
                © 2020 The Authors. Published by Elsevier B.V.

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                Research Article

                ans fluorescence,solid-state protein characterization,biofilms,hydration,decay associated spectra


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