Relevant bibliographies by topics / Α-crystallin

Academic literature on the topic 'Α-crystallin'

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Published: 4 June 2021
Last updated: 5 February 2022

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Journal articles on the topic "Α-crystallin"

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Selivanova, Olga M., and Oxana V. Galzitskaya. "Structural and Functional Peculiarities of α-Crystallin." Biology 9, no. 4 (April 23, 2020): 85. http://dx.doi.org/10.3390/biology9040085.

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α-Crystallin is the major protein of the eye lens and a member of the family of small heat-shock proteins. Its concentration in the human eye lens is extremely high (about 450 mg/mL). Three-dimensional structure of native α-crystallin is unknown. First of all, this is the result of the highly heterogeneous nature of α-crystallin, which hampers obtaining it in a crystalline form. The modeling based on the electron microscopy (EM) analysis of α-crystallin preparations shows that the main population of the α-crystallin polydisperse complex is represented by oligomeric particles of rounded, slightly ellipsoidal shape with the diameter of about 13.5 nm. These complexes have molecular mass of about 700 kDa. In our opinion, the heterogeneity of the α-crystallin complex makes it impossible to obtain a reliable 3D model. In the literature, there is evidence of an enhanced chaperone function of α-crystallin during its dissociation into smaller components. This may indirectly indicate that the formation of heterogeneous complexes is probably necessary to preserve α-crystallin in a state inactive before stressful conditions. Then, not only the heterogeneity of the α-crystallin complex is an evolutionary adaptation that protects α-crystallin from crystallization but also the enhancement of the function of α-crystallin during its dissociation is also an evolutionary acquisition. An analysis of the literature on the study of α-crystallin in vitro led us to the assumption that, of the two α-crystallin isoforms (αA- and αB-crystallins), it is αA-crystallin that plays the role of a special chaperone for αB-crystallin. In addition, our data on X-ray diffraction analysis of α-crystallin at the sample concentration of about 170–190 mg/mL allowed us to assume that, at a high concentration, the eye lens α-crystallin can be in a gel-like stage. Finally, we conclude that, since all the accumulated data on structural-functional studies of α-crystallin were carried out under conditions far from native, they cannot adequately reflect the features of the functioning of α-crystallin in vivo.
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Evans, Paul, Christine Slingsby, and B. A. Wallace. "Association of partially folded lens βB2-crystallins with the α-crystallin molecular chaperone." Biochemical Journal 409, no. 3 (January 15, 2008): 691–99. http://dx.doi.org/10.1042/bj20070993.

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Age-related cataract is a result of crystallins, the predominant lens proteins, forming light-scattering aggregates. In the low protein turnover environment of the eye lens, the crystallins are susceptible to modifications that can reduce stability, increasing the probability of unfolding and aggregation events occurring. It is hypothesized that the α-crystallin molecular chaperone system recognizes and binds these proteins before they can form the light-scattering centres that result in cataract, thus maintaining the long-term transparency of the lens. In the present study, we investigated the unfolding and aggregation of (wild-type) human and calf βB2-crystallins and the formation of a complex between α-crystallin and βB2-crystallins under destabilizing conditions. Human and calf βB2-crystallin unfold through a structurally similar pathway, but the increased stability of the C-terminal domain of human βB2-crystallin relative to calf βB2-crystallin results in the increased population of a partially folded intermediate during unfolding. This intermediate is aggregation-prone and prevents constructive refolding of human βB2-crystallin, while calf βB2-crystallin can refold with high efficiency. α-Crystallin can effectively chaperone both human and calf βB2-crystallins from thermal aggregation, although chaperone-bound βB2-crystallins are unable to refold once returned to native conditions. Ordered secondary structure is seen to increase in α-crystallin with elevated temperatures up to 60 °C; structure is rapidly lost at temperatures of 70 °C and above. Our experimental results combined with previously reported observations of α-crystallin quaternary structure have led us to propose a structural model of how activated α-crystallin chaperones unfolded βB2-crystallin.
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DERHAM, Barry K., and John J. HARDING. "Effects of modifications of α-crystallin on its chaperone and other properties." Biochemical Journal 364, no. 3 (June 15, 2002): 711–17. http://dx.doi.org/10.1042/bj20011512.

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The role of α-crystallin, a small heat-shock protein and chaperone, may explain how the lens stays transparent for so long. α-Crystallin prevents the aggregation of other lens crystallins and proteins that have become unfolded by ‘trapping’ the protein in a high-molecular-mass complex. However, during aging, the chaperone function of α-crystallin becomes compromised, allowing the formation of light-scattering aggregates that can proceed to form cataracts. Within the central part of the lens there is no turnover of damaged protein, and therefore post-translational modifications of α-crystallin accumulate that can reduce chaperone function; this is compounded in cataract lenses. Extensive in vitro glycation, carbamylation and oxidation all decrease chaperone ability. In the present study, we report the effect of the modifiers malondialdehyde, acetaldehyde and methylglyoxal, all of which are pertinent to cataract. Also modification by aspirin, which is known to delay cataract and other diseases, has been investigated. Recently, two point mutations of arginine residues were shown to cause congenital cataract. 1,2-Cyclohexanedione modifies arginine residues, and the extent of modification needed for a change in chaperone function was investigated. Only methylglyoxal and extensive modification by 1,2-cyclohexanedione caused a decrease in chaperone function. This highlights the robust nature of α-crystallin.
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Sathish, Hasige A., Hanane A. Koteiche, and Hassane S. Mchaourab. "Binding of Destabilized βB2-Crystallin Mutants to α-Crystallin." Journal of Biological Chemistry 279, no. 16 (February 3, 2004): 16425–32. http://dx.doi.org/10.1074/jbc.m313402200.

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Singh, Kamalendra, D. Zewge, B. Groth-Vasselli, and P. N. Farnsworth. "A comparison of structural relationships among α-crystallin, human Hsp27, γ-crystallins and βB2-crystallin." International Journal of Biological Macromolecules 19, no. 4 (December 1996): 227–33. http://dx.doi.org/10.1016/s0141-8130(96)01131-2.

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LINDNER, Robyn A., Teresa M. TREWEEK, and John A. CARVER. "The molecular chaperone α-crystallin is in kinetic competition with aggregation to stabilize a monomeric molten-globule form of α-lactalbumin." Biochemical Journal 354, no. 1 (February 8, 2001): 79–87. http://dx.doi.org/10.1042/bj3540079.

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In vivo, α-crystallin and other small heat-shock proteins (sHsps) act as molecular chaperones to prevent the precipitation of ‘substrate’ proteins under stress conditions through the formation of a soluble sHsp–substrate complex. Using a range of different salt conditions, the rate and extent of precipitation of reduced α-lactalbumin have been altered. The interaction of α-crystallin with reduced α-lactalbumin under these various salt conditions was then studied using a range of spectroscopic techniques. Under conditions of low salt, α-lactalbumin aggregates but does not precipitate. α-Crystallin is able to prevent this aggregation, initially by stabilization of a monomeric molten-globule species of α-lactalbumin. It is proposed that this stabilization occurs through weak transient interactions between α-crystallin and α-lactalbumin. Eventually a stable, soluble high-molecular-mass complex is formed between the two proteins. Thus it appears that a tendency for α-lactalbumin to aggregate (but not necessarily precipitate) is the essential requirement for α-crystallin–α-lactalbumin interaction. In other words, α-crystallin interacts with a non-aggregated form of the substrate to prevent aggregation. The rate of precipitation of α-lactalbumin is increased significantly in the presence of Na2SO4 compared with NaCl. However, in the former case, α-crystallin is unable to prevent this aggregation and precipitation except in the presence of a large excess of α-crystallin, i.e. at mass ratios more than 10 times greater than in the presence of NaCl. It is concluded that a kinetic competition exists between aggregation and interaction of unfolding proteins with α-crystallin.
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Crabbe, M. J., and D. Goode. "α-Crystallin: chaperoning and aggregation." Biochemical Journal 297, no. 3 (February 1, 1994): 653–54. http://dx.doi.org/10.1042/bj2970653.

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Merck, K. B., W. A. de Haard-Hoekman, H. Bloemendal, and W. W. de Jong. "Protein engineering of α-crystallin." Experimental Eye Research 55 (September 1992): 165. http://dx.doi.org/10.1016/0014-4835(92)90772-k.

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Nagaraj, Ram H., Rooban B. Nahomi, Niklaus H. Mueller, Cibin T. Raghavan, David A. Ammar, and J. Mark Petrash. "Therapeutic potential of α-crystallin." Biochimica et Biophysica Acta (BBA) - General Subjects 1860, no. 1 (January 2016): 252–57. http://dx.doi.org/10.1016/j.bbagen.2015.03.012.

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Narberhaus, Franz. "α-Crystallin-Type Heat Shock Proteins: Socializing Minichaperones in the Context of a Multichaperone Network." Microbiology and Molecular Biology Reviews 66, no. 1 (March 2002): 64–93. http://dx.doi.org/10.1128/mmbr.66.1.64-93.2002.

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SUMMARY α-Crystallins were originally recognized as proteins contributing to the transparency of the mammalian eye lens. Subsequently, they have been found in many, but not all, members of the Archaea, Bacteria, and Eucarya. Most members of the diverse α-crystallin family have four common structural and functional features: (i) a small monomeric molecular mass between 12 and 43 kDa; (ii) the formation of large oligomeric complexes; (iii) the presence of a moderately conserved central region, the so-called α-crystallin domain; and (iv) molecular chaperone activity. Since α-crystallins are induced by a temperature upshift in many organisms, they are often referred to as small heat shock proteins (sHsps) or, more accurately, α-Hsps. α-Crystallins are integrated into a highly flexible and synergistic multichaperone network evolved to secure protein quality control in the cell. Their chaperone activity is limited to the binding of unfolding intermediates in order to protect them from irreversible aggregation. Productive release and refolding of captured proteins into the native state requires close cooperation with other cellular chaperones. In addition, α-Hsps seem to play an important role in membrane stabilization. The review compiles information on the abundance, sequence conservation, regulation, structure, and function of α-Hsps with an emphasis on the microbial members of this chaperone family.
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Dissertations / Theses on the topic "Α-crystallin"

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Knight, Grady C. "The molecular chaperone α-crystallin protects proteins from UV-induced aggregation." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30486.

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Muir, Matthew Stewart. "Proteomics of the ovine cataract." Diss., Lincoln University, 2008. http://hdl.handle.net/10182/792.

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The lens of the eye needs to be completely transparent in order to allow all light entering the eye to reach the retina. This transparency is maintained by the highly ordered structure of the lens proteins the crystallins. Any disruption to the lens proteins can cause an opacity to develop which is known as cataract. During cortical cataract formation there is increased truncation of the lens crystallins. It is believed that overactivation of calcium-dependent cysteine proteases, the calpains, is responsible for the increased proteolysis of the crystallins seen during cataractogenesis. Within the ovine lens there are three calpains, calpain 1, 2 and the lens specific calpain Lp82. The aim of this thesis was to determine the changes in the lens proteins during ageing and cataractogenesis, and to establish the role of the calpains in these processes. Calpain 1 and 2 were purified from ovine lung and Lp82 was purified from lamb lenses using chromatography. Activity and presence of the calpains was determined by using the BODIPY-FL casein assay, gel electrophoresis, Western blot and casein zymography. Changes in the lens proteins, specifically the crystallins, were visualised using two-dimensional electrophoresis (2DE). Lenses from fetal, 6 month old and 8 year old sheep were collected, as well as stage 0, 1, 3 and 6 cataractous ovine lenses. The proteins from the lenses were separated into the water soluble and urea soluble fractions and analysed by 2DE. Mass spectrometry was used to determine the masses and therefore modifications of the crystallins. Finally, the individual crystallins were separated using gel filtration chromatography and incubated with the purified calpains in the presence of calcium. The extent of the proteolysis was visualised using 2DE and truncation sites determined by mass spectrometry. Purification of the calpains resulted in samples that were specific for each calpain and could be used in further experiments. 2DE analysis showed that there were changes to the crystallins during maturation of the lens. The α-crystallins become increasingly phosphorylated as the lens ages and a small amount becomes truncated. The β-crystallins were also modified during ageing by truncation and deamidation. When crystallins from cataractous lenses were compared using 2DE there were changes to both the α- and β-crystallins. The α-crystallins were found to be extensively truncated at their C-terminal tail. Four of the seven β-crystallins, βB1, βB3, βB2 and βA3, showed increased truncation of their N-terminal extensions during cataract formation. All three calpains truncated αA and αB-crystallin at their C-terminal ends after incubation. Calpain 2 and Lp82 each produced unique αA-crystallin truncations. All three calpains truncated βB1 and βA3 and calpain 2 also truncated βB3. When the truncations from the calpain incubations were compared to those seen during cataract formation, many of the truncations were found to be similar. Both the unique truncations from calpain 2 and Lp82 were found in cataractous lenses, with the Lp82 more obvious in the 2DE. The β-crystallin truncations found after incubation with the calpains were similar to those found during cataractogenesis. In conclusion this study documents the changes to the ovine lens during maturation and cataractogenesis and indicates a role for the calpain family in the increased proteolysis observed in the ovine cataract.
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Al, Hashmi Salim M. "Studies on the stress responses of M. tuberculosis : tmRNA and α-crystallins." Thesis, University of Surrey, 2016. http://epubs.surrey.ac.uk/811054/.

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Mycobacterium tuberculosis remains a major human health problem killing millions of people around the world. Therefore, the need for an in depth understanding of its pathogenicity is very important to enable rational development of new control strategies.  Not all M. tuberculosis infected individuals progress to active disease at the time of primary infection as some carry an asymptomatic persistent infection that may reactivate later in life to cause disease. Despite a great deal of M. tuberculosis research, the ability of M. tuberculosis to cause long-term persistent infection in immune-competent hosts is poorly understood. When M. tuberculosis is inside the body it faces many environmental stress conditions including hypoxia, starvation and oxidative stress that damage proteins, DNA and other molecules. Gene expression studies have identified many bacterial genes that are differentially regulated when M. tuberculosis is subjected to such environmental stresses. This thesis focusses on three of these genes, the ssrA gene, which encodes the tmRNA molecule involved in ribosome recycling and degradation of denatured proteins, and two genes encoding -crystallin molecular chaperones (acr1 and acr2). This study was designed to achieve two aims: (1) to examine the role of tmRNA in translational control and protein homeostasis in stressed mycobacteria; and (2) to understand the roles of Acr1 and Acr2 in the stress response of M. tuberculosis and to reveal the degree of redundancy between them. In this thesis it was shown that ssrA/tmRNA is essential for bacterial viability as it was not possible to delete the gene unless a second fully functional copy was introduced elsewhere in the genome. The results suggested that the protease tagging function of tmRNA is essential alongside its role in ribosome recycling. A recombinant His-tagged tmRNA was expressed in the mycobacteria in an attempt to identify if tmRNA is directly involved in the translation of stress proteins. Expression of the His-tagged tmRNA was detrimental to the cell and appeared to preclude successful tagging of tmRNA substrate polypeptides. Thus there was insufficient evidence to support the hypothesis. Ultrastructural localisation of Acr1 and Acr2 by immuno-electron microscopy and Western blotting of subcellular fractions of mycobacteria showed that Acr1 and Acr2 were localised in different parts of the cell. Assay of the phenotypes of single and double deletion mutants of Acr1 and Acr2 in different in vitro conditions failed to show any evidence that the two chaperones are functionally redundant. Indeed, experiments on intracellular infection of macrophages showed no phenotypic consequences resulted from loss of Acr1 but deletion of Acr2 resulted in an altered cytotoxic effect on the host cell.
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SHEN, WEI-TING, and 沈蔚婷. "The stability of the α-crystallin." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/78rsjg.

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碩士
國防醫學院
生物化學研究所
102
The lenticular α-crystallin consisits of two 20-kDa polypeptide chains, αA andαB, which belongs to the small heat shock protein family. They have 57% sequence homology among themselves. In this study, the change in structure, chaperone activity, complex size and thermostability of αA and αB- homooligomer and their heterooligomer in different ratio incubated at 37℃ were investigated. The result showed that heterooligomer of αA and αB-crystallin have about 29% smaller than αB-homooligomer in exposed hydrophobic region as measured by ANS binding. Thermalstability analysis showed the Tm values of heterooligomer in the ratio of 1:3,3:1 and 1:1 were about 83.5℃,91.6℃ and 92.6℃,respectively which were between the Tm values of αA and αB-homooligomer, 70.8℃ and 92.8℃ respectively.The CD data showed about 4% increased and 6% decreased in α-helix and β-sheet content respectively,as comparing the heterooligomer in ratio of 3:1 with αA-crystallin homooligomer and showed about 4% increased and 4% decreased in the contents as compared with αB-homooligomer.The heterooligomer in ratio of 3:1,1:1 and 1:3 showed about 90%, 84% and 74%,respectively,protection of hASL from thermodenaturation. The protection ability of αA-crystallin homooligomer was about 92.3% higher than the αB- homooligomer(34.5%).The heterooligomer that incubated for 24h then through freezing-thawing cycle showed higher stability than that incubated for 2 hours.The results showed that slow freezing and thawing rate induces damage in protein stability.The protein concentration remained after freez-thaw forαA and αB- homooligomer and heteroligomer in ratio of 1:1,1:3,1:7,3:1and 7:1 were 79.8%、88.4%、96.5%、88.2%、97.9%、91.2% and 93.5%,respectively.The heterooligomer showed a better stability than αA and αB- homooligomer.
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Li, Rongyu [Verfasser]. "Protease-activated receptor 2 and α-crystallin [alpha-crystallin] : interactions and functional implications / von Rongyu Li." 2010. http://d-nb.info/1010327070/34.

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Yu-Wen, Cheng, and 鄭喻文. "Comparison of recombinant human argininosuccinate lyase and recombinant goose δ-crystallin interaction with goose α-crystallin." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/23577020140948421566.

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碩士
國防醫學院
生物化學研究所
96
Taxon-specific -crystallin, the major soluble protein component of the avian and reptilian eye lens, is considered to play a structural role in maintaining a high refractory index while ensuring transparency. However, the most astounding relationship is an evolutionary strategy of gene sharing that the taxon specific crystallins seems to be present in which the same gene product is utilized in dual function as a lens crystallin and as an enzyme in non-lens tissues. These sequence similarities such as the -crystallins are closely related to argininosuccinate lyase. -Crystallin and ASL are a superfamily of metabolic enzymes that catalyze the reversible cleavage of argininosuccinate to arginine and fumarate. ASL is one of the cytosolic enzymes of the urea cycle in ureagenic animals. -Crystallin is the member of the small heat shock protein family and function as a molecular chaperone-like activity in preventing the non specific thermal aggregation of lens proteins. In addition, -Crystallin consists of two polypeptide chains, A and B. In the present study, we used the temperature-dependent to investigate the effect of recombinant goose A- and B-crystallins on recombinant goose -crystallin and HASL. At 25°C, the addition of A and B led to 103% and 130% increase in the specific activity of HASL, respectively. It is found that the optimal temperature of HASL was at 40°C brought about 149% in the specific activity, whereas the specific activity was about 7% at 60°C. In contrast, HASL is stabled up to approximately 50°C in the presence of A and B, and even has about 17% and 31% at 60°C, respectively. Conditions for incubation of -crystallin and HASL were set at room temperature for 1 hr that is determined through time and temperature dependent assays of ASL activity in the presence of A and B. The tryptophan fluorescence experiments of HASLWT on A show significantly decreased at about 30% ~ 50%. Under the temperature-dependent conditions, the protection effect of B on -crystallin is more remarkable than A. In addition, calibrated S-200 size exclusion chromatography revealed that -crystallin and HASL in the presence of B form a stable complex.
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Jiahn-Shing, Lee, and 李建興. "α-Crystallin Possessing Molecular Chaperone Activity: Structural and Functional Study." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/22537764102452161462.

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博士
長庚大學
臨床醫學研究所
86
ABSTRACT: Recently, α-crystallin is regarded as a member of small heat shock proteins. Joseph Horwitz also demonstrated in 1992 that it can act as a molecular chaperone to prevent thermal aggregation of other crystallins and enzymes. The main purpose of this thesis is to explore the relationship between the conformational states of α-crystallin and its chaperone activity. We have first determined the cDNA sequence of αB-crystallin from porcine lenses by cDNA cloning technique. It contains one complete full-length reading frame of 525 base pairs, covering a protein sequence of 175 amino acids. Further expression of this αB subunit chain in E.coli generated a polypeptide which can cross-react with the antiserum against the native αB-crystallin, and also possesses chaperone activity. The next, a comparative study was conducted to analyze the chaperone activity of α-crystallin from bovine (mammal), duck (bird), caiman (reptile), and shark (fish), respectively. Our results show that the difference in the chaperone activity of α-crystallins among different species is relatively small, indicative of the evolutionary conservation in function similar to that revealed by their conserved protein structure. α-Crystallins of different species also show no substrate specificity in their chaperone activity. In addition to its anti-heat shock property, α-crystallin can also act as a chaperone against UV-irradiation, H2O2-oxidation, and other stress. However, in terms of stoichiometry, such protective ability is not so efficient as that under thermal stress. Part of the reason is the photochemical susceptibility of α-crystallin to UV-irradiation. The UV-induced destruction was found to correlate with its loss of chaperone activity. Similarly, there is some age-dependent change in the chaperone activity of α-crystallin obtained from a young and normal lens as compared to an old and cataractous lens. Thus, the gradual loss of chaperone activity of α-crystallin upon aging is probably through an accumulative event of long term exposure to UV light, which may also shed light on human cataract formation. The mechanism underlying the chaperone activity of α-crystallin involves preferential binding of the partially denatured substrate protein to α-crystallin, and the formation of a stable complex. We have demonstrated that the binding of substrate proteins to α-crystallin by short-term pre-incubation may mimic the in vivo conditions of crystallin association. Under such conditions, the chaperone activity of α-crystallin to inhibit ultraviolet-, or oxidation-induced protein aggregation can be greatly enhanced. Thus, the presence ofα-β and α-γ complex in vivo may be relevant to the process of maintaining lens transparency. From the result of circular dichroism and other studies, it is generally accepted that the secondary structure of α-crystallin consists predominantly of β-sheets. A minor but detectable perturbation in the tertiary structure of α-crystallin occurs at above 30℃, which correlates with the extent of exposure of its hydrophobic surfaces. Such increase in surface hydrophobicity also correlates with its increased chaperone activity. These results indicate that hydrophobic interaction play a major role in the chaperone action of α-crystallin. Another thermotropic transition in the secondary structure of α-crystallin occurs at a range between 50 and 70℃, which is largely reversible. However, the heat-induced changes in secondary structure shows a relatively little effect on the chaperone activity of α-crystallin. In summary, α-crystallin is not only a major structural protein of the lens but may also play an important "house-keeping" role as a molecular chaperone. Both the conformational state of α-crystallin and the association complex with its substrate may contribute to a generalized mechanism of its chaperone function. Such results may provide us a new direction in the study of cataractogenesis and its treatment in the future.
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Chis, Roxana. "Elucidation of the Protective Mechanism of α Crystallin B in Cardiomyocytes." Thesis, 2012. http://hdl.handle.net/1807/32233.

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α-Crystallin B (cryAB) is the most abundant small heat shock protein in cardiomyocytes (CMs), where it has been shown to have potent anti-apoptotic properties. The mechanism by which cryAB prevents apoptosis has not been fully characterized. Therefore, I was interested in elucidating its protective mechanism in CMs. I identified its sub-cellular localization and its binding interactors following H2O2 exposure. I found that cryAB is found in the cytosol under control conditions and that following H2O2 exposure it becomes phosphorylated and translocates to the mitochondria. CryAB silencing resulted in increased apoptosis levels in CMs. Co-immunoprecipitation revealed an apparent increased interaction of cryAB and PcryAB with mitochondrial VDAC, caspase 12 and uncleaved caspase 3 in stressed hearts relative to controls. These results suggest that the cardio-protective effects of cryAB are mediated by its translocation to the mitochondria and its interaction with VDAC, caspase 12 and caspase 3 following exposure to H2O2.
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Lin, Tsuen-Pei, and 林春霈. "Characterization of Thermal-Induced High Molecular Weight Aggregate of Rat Lens α-Crystallin." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/s33s4j.

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碩士
國立成功大學
化學系碩博士班
91
α-Crystallin and high molecular weight aggregate (HMWA) were isolated from four weeks old Rat lenses. α-Crystallin was further heated at various temperatures (50-60℃) to induce thermal aggregation of HMWA, which was used to make a compare with in vivo HMWA. Spectroscopic measurement were performed to study the structure and functionality of both HMWA. Conformation differences of native HMWA were suggested based on the data of increased trytophan (Trp), non- tryptophan (non-Trp), 1-anilino- naphthalene-8-sulfonic acid (ANS), and 2-(4’-maleimidylanilino) naphthalene-6-sulfonic acid (MIANS) fluorescence intensity as well as the increased far-UV and near-UV circular dichroism (CD). These results indicated that native HMWA was more hydrophobic than α-crystallin, possibly resulting from the partial unfolding of native α-crystallin. Gel filtration chromatography showed that α-crystallin heat-induced HMWA prepared by preheating at 60℃ for an hour with the same molecular weight as that of in vivo HMWA. Trp, ANS, and MIANS fluorescence as well as far-UV CD measurements indicated that heat-induced HMWA and in vivo HMWA shared structural similarity, which further suggested the same aggregation mechanism. Chaperone-like activity was observed toward the aggregation of dithiothreitol (DTT)-induced insulin B-chain show that α-crystallin preheated at 50℃ has better activity than α-crystallin and native HMWA. With the increase of preheating temperature, the activity of α-crystallin decreased and it was observed that under 60℃, it was less active than native HMWA. The correlation between the ANS fluorescence and the chaperone-like activity suggests that surface hydrophobicity was not the sole determinant of the chaperone function of the α-crystallin. Cysteine modification of α-crystallin was carried out using 10 mM and 50 mM β-mercaptoethanol followed by heating at 60℃ for an hour, then was subjected to gel filtration and SDS-PAGE. Heat-induced HMWA remained formed from 50 mM modification of α-crystallin, whereas there was no disulfide bond was observed, indicated that disulfide bond formation was not the (main) factor leading to the formation of HMWA, at least in heat-induced HMWA formation. Our study suggests that heat-induced HMWA proceed similar mechanism as that of in vivo HMWA via partial unfolding, however, the unfolding process may differ as to show different non-Trp fluorescence, near-UV CD and chaperone-like activity as well.
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an, chuang sheng, and 莊勝安. "The Study of Rat Lens α-crystallin Under the Effects of Mg2+ and pH." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/76335158433239884381.

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碩士
國立成功大學
化學系
87
Fluoroscence spectroscopy, circular dichroism spectroscopy (CD), and fast protein liquid chromatography (FPLC) have been used to study the aggregation of rat lens α-crystallin under the effects of Mg2+, trifluoroethanol and pH. The chaperone activity of α-crystallin toward ditiothreitol-induced insulin aggregation was measured under various concentration of Mg2+ and the activity was correlated with the structural change of α-crystallin. It was observed that ANS and tryptophan fluorescence emissions increased as the concentration of Mg2+ increased, indicating α-crystallin underwent a structural change with more hydrophobic region exposed. However, the change of chaperone activity did not correlate with the observed increase of fluorescence, suggesting that surface hydrophobicity and microenvironment of tryptophan are not necessarily relate to the chaperone function of α-crystallin under the influence of Mg2+. The aggregation study using FPLC showed a 20 kDa and a 540 kDa fractions, and the ratio of 20 kDa to 540 kDa was Mg2+ concentration dependent. Interestingly, re-chromatography of the 540 kDa fraction also gave a 20 kDa and a 540 kDa fraction, whereas the 20 kDa fraction remained no change after re-chromatographed. The aggregation also showed pH dependent. It was found that only 20 kDa fraction was observed at pH 4 and 5, while at pH 9.0 two fractions at 60 kDa and 690 kDa were observed. In the presence of trifluoroethanol, α-crystallin solution started to go opaque as the concentration of trifluoroethanol reached 10%. As trifluoroethanol concentration increased (less that 10 %), spectroscopic studies showedα-crystallin underwent a strnctural change, including loss of secondary structure, enhancement of tryptophan fluorescence and decrease of surface hydrophobicity.
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Book chapters on the topic "Α-crystallin"

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Chepelinsky, Ana B., Eric F. Wawrousek, Robert A. Dubin, Cynthia J. Jaworski, Joan B. McDermott, and Joram Piatigorsky. "Transcriptional Control of the α-Crystallin Gene Family." In Presbyopia Research, 5–12. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4757-2131-7_1.

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Groenen, Patricia J. T. A., Karin B. Merck, Wilfried W. De Jong, and Hans Bloemendal. "Structure and modifications of the junior chaperone α-crystallin." In EJB Reviews 1994, 165–83. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-79502-2_13.

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Chowdhury, Aritra, Rajat Banerjee, and K. P. Das. "Biophysical Studies of a Micellar Protein α-Crystallin by Fluorescence METHODS." In Encyclopedia of Biocolloid and Biointerface Science 2V Set, 737–52. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119075691.ch60.

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Farnsworth, Patricia N., Thomas F. Kumosinski, Gregory King, and Barbara Groth-Vasselli. "Computer-Generated Working Models of α-Crystallin Subunits and Their Complex." In ACS Symposium Series, 123–38. Washington, DC: American Chemical Society, 1994. http://dx.doi.org/10.1021/bk-1994-0576.ch009.

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Sax, Charistina M., and Joram Piatigorsky. "Expression of the α-Crystallin/Small Heat-Shock Protein/Molecular Chaperone Genes in the Lens and other Tissues." In Advances in Enzymology - and Related Areas of Molecular Biology, 155–201. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2006. http://dx.doi.org/10.1002/9780470123157.ch5.

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Mikami, Koichi. "Catalytic Asymmetric Synthesis of Diastereomeric α- or β-CF3Liquid Crystalline Molecules." In ACS Symposium Series, 255–69. Washington, DC: American Chemical Society, 1999. http://dx.doi.org/10.1021/bk-2000-0746.ch018.

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Taleb, Ilhem N., Majda Rahal-Sekkal, Jean-Pierre Huvenne, and Gérard Vergoten. "Vibrational normal modes calculations of the α-L-Fucose molecule in the crystalline state." In Spectroscopy of Biological Molecules: New Directions, 429–30. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4479-7_193.

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Sreekumar, Parameswaran G., David R. Hinton, and Ram Kannan. "Glutathione Metabolism and Its Contribution to Antiapoptotic Properties of α-Crystallins in the Retina." In Studies on Retinal and Choroidal Disorders, 181–201. Totowa, NJ: Humana Press, 2012. http://dx.doi.org/10.1007/978-1-61779-606-7_9.

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Daly, William H., Ioan I. Negulescu, Paul S. Russo, and Drew S. Poche. "Side-Chain Crystallinity and Thermal Transitions in Thermotropic Liquid-Crystalline Poly(γ-alkyl-α,L-glutamate)s." In ACS Symposium Series, 292–99. Washington, DC: American Chemical Society, 1992. http://dx.doi.org/10.1021/bk-1992-0493.ch023.

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Parthasarathy, R., Sanjeev Chaturvedi, and Kuantee Go. "Design of crystalline helices of short oligopeptides as a possible model for nucleation of the α-helix." In Proteins, 321–24. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-010-9063-6_47.

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Conference papers on the topic "Α-crystallin"

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Cai, Jun, Qing Ruan, Song Han, Zhijuan Chen, Brian K. Law, and Wengou Jiang. "Abstract LB-4: Mechanisms by which the unfolded protein response/α-Basic-crystallin (CRYAB) regulates VEGF signaling of tumor endothelial cells." In Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL. American Association for Cancer Research, 2011. http://dx.doi.org/10.1158/1538-7445.am2011-lb-4.

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Kingma, Kathleen J., Russell J. Hemley, David R. Veblen, and Ho-kwang Mao. "High-pressure crystalline transformations and amorphization in α-quartz." In High-pressure science and technology—1993. AIP, 1994. http://dx.doi.org/10.1063/1.46126.

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Waltermire, Scott W., Juekuan Yang, Deyu Li, and Terry T. Xu. "Thermal Conductivity of α-Tetragonal Boron Nanoribbons." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88347.

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Elemental boron has many interesting properties, such as high melting point, low density, high hardness, high Young’s modulus, good oxidation resistance, resulting from its complex crystalline structure from its electron-deficient nature. Boron forms complex crystalline structures according to the various arrangements of B12 icosahedra in the lattice, such as α (B12)- and β (B105)-rhombohedral and α (B50)- and β (B196)-tetragonal boron polymorphs, among others. Even though considerable materials research has been conducted over the past half century on boron and boron-based compounds, investigating their unique structures and corresponding properties, our understanding of this complex class of materials is still poor, compared to some other well-studied materials with much simpler structures such as silicon. Thermal transport studies through bulk boron have been performed mainly on β-rhombohedral and amorphous boron, because of the difficulty to grow high quality bulk α-rhombohedral boron samples [1–3]. Some efforts have been made to measure B12As2, B12P2, AlB12 samples that have an α-rhombohedral form [2,3]. There is almost no information available on α-tetragonal boron. However, Slack predicted the thermal conductivity of α-boron should be ∼200 W/m-K at room temperature, which is 1/2 that of copper. Large phonon mean free path has been predicted for α-boron (from ∼200 nm at room temperature to 6 nm at the Debye temperature), which could lead to interesting thermal transport properties for low dimensional boron structures.
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Veiller, L., JP Crocombette, C. Meis, and D. Ghaleb. "Molecular Dynamics Simulation of the Alpha-Recoil Nucleus Displacement Cascade in Zirconolite." In ASME 2001 8th International Conference on Radioactive Waste Management and Environmental Remediation. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/icem2001-1290.

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Abstract Zirconolite (CaZrTi2O7) has been proposed as a crystalline ceramic host for the long-term disposal of actinides extracted from high-level nuclear waste (e.g. France) and from excess weapons-grade plutonium (e.g. USA). The disintegration of radionuclides induces modifications of the crystalline structure. During α-decay of actinides, localized cascades of displaced atoms occur primarily because of ballistic collisions in the material from the emitted α-recoil nuclei. Under α-decay irradiation, zirconolite undergoes a crystalline to amorphous transformation, which is associated to a volume expansion. We have focused our study on the understanding of radiation-induced structural changes at the atomic level in this ceramic. Molecular Dynamics (MD) has been used in the simulation of displacement cascades in zirconolite. Original Buckingham pair potentials have been established for zirconolite to characterize the two body short-range interactions between different ionic pairs. We present the potential parameters fitted to the structural equilibrium properties of the crystal. This fitting reproduces the characteristics of the cell parameters of zirconolite within 4% and gives reasonable values for the bulk modulus and the specific heat. The MD method is applied to determine the threshold displacement energies for the various sublattices. Finally, we have modelled the effects of displacement cascades in zirconolite, due to the α-recoil nuclei. For that purpose, two MD simulations of high recoil kinetic energies (2 and 6 keV) were performed. The preliminary results show that the complex matrix zirconolite tends to a structural disordering for high PKA energy values although a partial recrystallization step is observed during the energy dissipation.
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Keke, Anete, and Ingmars Cinkmanis. "α-amylase activity in freeze-dried and spray-dried honey." In Research for Rural Development 2020. Latvia University of Life Sciences and Technologies, 2020. http://dx.doi.org/10.22616/rrd.26.2020.017.

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Honey is a naturally supersaturated sugar solution, which tends to crystallize. The crystallization of honey can lead to unwanted fermentation that can have a negative impact to honey quality. The production of honey powder could be an alternative method to prevent honey from fermentation. Honey powder could be used as alternative substitute to liquid honey that would allow to use this product more widely in the food industry. α-amylase activity is one of the most important parameters to evaluate the quality of honey. The aim of this study was to investigate the effect of freeze-drying and spray-drying on honey α-amylase activity. Detection of α-amylase activity was carried out by spectrophotometric method. High-performance liquid chromatography was used to determine the content of hydroxymethylfurfural in the powders. The obtained results showed that both drying methods had a negative impact to the enzyme activity in the samples. The lowest activity of α-amylase (8.3 DN) was measured in the spray-dried honey powder. Concentration of hydroxymethylfurfural (HMF) in the powders did not exceed required concentration 40 mg kg-1.
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Sun, L., C. C. Berndt, R. S. Lima, A. Kucuk, and K. A. Khor. "Effects of Spraying Parameters on Phase Formation and Distribution in Plasma-Sprayed Hydroxyapatite Coatings." In ITSC 2000, edited by Christopher C. Berndt. ASM International, 2000. http://dx.doi.org/10.31399/asm.cp.itsc2000p0803.

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Abstract Calcined spray-dried hydroxyapatite (Ca10(PO4)(OH)6; i.e., HA) powders were atmospherically plasma sprayed (APS) using various process parameters. The resulting phases within the coating surface and the interface between the coating and the substrate were analyzed using X-ray diffraction (XRD) methods. This XRD revealed the presence of both amorphous (i.e., amorphous calcium phosphate: ACP) and crystalline phases. The crystalline phases included both HA and some impurity phases from the decomposition of HA, such as tricalcium phosphate (α-TCP and β-TCP), tetracalcium phosphate (TTCP) and calcium oxide (CaO). The crystallinity of HA decreased with increasing spray power and stand-off distance (SOD). The percentage of all impurity phases increased with the spray power. The percentage of both TCP and TTCP decreased with the SOD while the CaO percentage increased. In addition, the percentage of ACP and CaO were higher in the interface than at the surface of the coating while the percentage of TCP and TTCP exhibited the opposite effect.
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Daun, K. J. "Thermal Accommodation Coefficients Between Nitrogen and Soot in Laser-Induced Incandescence Experiments." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-69282.

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Time-resolved laser-induced incandescence demands detailed knowledge of the thermal accommodation coefficient, but to date little is understood about the gas/surface scattering physics underlying this parameter. We present a molecular dynamics (MD) simulation that models nitrogen molecules as rigid rotors and soot as crystalline graphite at 3000 K. A Monte Carlo integration over incident gas molecular speeds and surface atomic vibrational phases yields a simulated thermal accommodation coefficient that matches the experimentally-measured value. The MD simulation is then extended to assess how α changes with gas temperature, and finally to define a Cercingnani-Lampis-Lord scattering kernel.
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Kato, Yoko. "The Role of Protein as a Deformation Controller in Cellulose Tissue." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89313.

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The tunic of Halocynthia roretzi is composed of cellulose Iβ, mostly in crystalline form. It was recently revealed that the tunic can actively deform in response to mechanical stimuli and acetylcholine and that the tunic has F-actin, elastic fibers, acetylcholinesterase, and neurofilaments, which are involved in this process. Most of the hemocytes in the tunic secrete an enzyme whose substrate is the same as that of α-chymotrypsin; however, the enzyme’s role has not yet been determined. In this study, it was hypothesized that the enzyme hydrolyzes the protein in the tunic to induce tunic deformation. The results show that administration of α-chymotrypsin results in deformation of the tunic in an inward direction. Tunic deformation can be induced by the secretion of hemocytes due to greater hydrolysis of protein in the inner rather than outer regions. The deformation pattern is the same as that induced by both mechanical stimuli and acetylcholine. Moreover, stimulation with an electrical field (3.4 × 102 V/m), which is too weak to deform cellulose, still causes tunic deformation, indicating involvement of the nervous system. These characteristics will be helpful for the design of an active composite material containing cellulose.
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Armstrong, Nicholas, Peter A. Lynch, Sitarama R. Kada, Pavel Cizek, Justin A. Kimpton, and Ross A. Antoniou. "Bayesian Analysis of In-Situ High-Resolution X-Ray Diffraction Synchrotron Experiments of Ti-6Al-4V Specimens Undergoing Tensile Loading." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91230.

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Abstract Linking the accumulation of microstructural damage prior to crack initiation to the lifing of aero-engines components would help to better predict the time that a component spends in this crack initiation stage. We present the results and analysis of in-situ high-resolution X-ray diffraction (XRD) experiments of a Ti-6Al-4V specimen that experienced tensile loading using medium energy synchrotron X-rays (≤ 21 keV) carried out at the Australian Synchrotron. The XRD analysis characterised XRD line-broadening due to the build-up of dislocations and the formation of crystallites in α- and β-Ti-6Al-4V specimens. Using Bayesian XRD analysis methods, the density, spatial arrangement of dislocations, and crystallite size information for α- and β-phases of the Ti-6Al-4V was extracted from the XRD line-profiles, as a function of applied load. The XRD analysis was then compared and validated with transmission electron microscopy (TEM) analysis of the specimen before and after the loading. Comparison of the TEM and XRD analysis reveals broad agreement in terms of the microstructural damage of Ti-6Al-4V specimens.
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Abdul-kareem, Asma Abdulgader, Noura AlSanari, Amal Daifallah, Radwa Mohamed, Jolly Bhadra, Deepalekshmi Ponnamma, and Noora Al-Thani. "Piezoelectric Nanogenerators based on Pvdf-Hfp/Zno Mesoporous Silica Nanocomposites for Self-Powering Devices." In Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0054.

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Due to the rising global concern over energy catastrophe and environmental issues, attention has been diverted towards future energy. In recent times, rechargeable power and renewable energy sources have been considered as an attractive substitute for resolving the future environmental problems. Among them, mechanical energy is one of the most abundant energy sources, and easily transformable to other useful energy forms, such as electrical energy. For such purposes, piezoelectric materials with ability to convert the mechanical energy generated by various activities into electrical energy. In this research work, we have investigated the morphology, structure and piezoelectric performances of neat polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), PVDF-HFP/ZnO, PVDFHFP/ Mesoporous silica, PVDF-HFP 1% and PVDF-HFP 3% ZnO-Mesoporous silica nanofibers, fabricated by electrospinning. Both SEM and TEM images of ZnO nanoparticles shows formation of uniform flake of about 5nm diameter and Mesoporous silica shows uniform spherical morphology with average diameter of 5 μm. EDX plot justifies the presences of Zn, O and Si. An increase in the amount of crystalline β-phase of PVDF-HFP has been observed with the introduction of ZnO and mesoporous silica in the PVDF-HFP matrix are observed in FTIR spectra. All the XRD peaks observed in neat PVDF has the strongest intensity compared to rest of the other XRD peaks of polymer nanocomposite. The XRD spectra of all the nanocomposites have peaks at 17.8°, 18.6° correspond to α- crystalline phase, the peaks observed at 19°, 20.1° correspond to the γ- crystalline phase, and the peak at 20.6° corresponds to the β- crystalline phase. The flexible nanogenerator manipulated from the polymer nanocomposite with 1% ZnO-Mesoporous silica exhibits an output voltage as high as 2 V compared with the neat PVDF-HFP sample (~120 mV). These results indicate that the investigated nanocomposite is appropriate for fabricating various flexible and wearable self-powered electrical devices and systems.
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