@article { ISI:000245984200011, title = {Bile salt hydrolase, the member of Ntn-hydrolase family: differential modes of structural and functional transitions during denaturation}, journal = {IUBMB Life}, volume = {59}, number = {2}, year = {2007}, month = {FEB}, pages = {118-125}, publisher = {TAYLOR \& FRANCIS INC}, type = {Article}, address = {325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA}, abstract = {

Conformational transitions and functional stability of the bile salt hydrolase (BSH; cholylglycine EC: 3.5.1.24) from Bifidobacterium longum (BlBSH) cloned and expressed in E. coli were studied under thermal, chemical and pH-mediated denaturation conditions using fluorescence and CD spectroscopy. Thermal and Gdn-HCl-mediated denaturation of BlBSH is a multistep process of inactivation and unfolding. The inactivation and unfolding of the enzyme was found to be irreversible. Enzyme activity seems sensitive to even minor conformational changes at the active site. Thermal denaturation as such did not result in any insoluble protein aggregates. However, on treating with 0.25-1 M Gdn-HCl the enzyme showed increasing aggregation at temperatures of 40-55 degrees C indicating more complex structural changes taking place in the presence of chemical denaturants. The enzyme secondary structure was still intact at acidic pH (pH 1-3). The perturbation in the tertiary structure at the acidic pH was detected through freshly formed solvent exposed hydrophobic patches on the enzyme. These changes could be due to the formation of an acid-induced molten globule-like state.

}, keywords = {Aggregation, Bile salt hydrolase, molten-globule, Unfolding}, issn = {1521-6543}, doi = {10.1080/15216540701245014}, author = {Kumar, R. Suresh and Suresh, C. G. and Brannigan, James A. and Dodson, Guy G. and Gaikwad, Sushama M.} } @article { ISI:000280597500004, title = {Conformational and functional transitions in class II alpha-mannosidase from aspergillus fischeri}, journal = {Journal of Fluorescence}, volume = {20}, number = {4}, year = {2010}, month = {JUL}, pages = {827-836}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

The conformational transitions in an oligomeric and high molecular weight class II alpha-mannosidase from Aspergillus fischeri were examined using fluorescence and CD spectroscopy under chemical, thermal and acid denaturing conditions. The enzyme lost the activity first and then the overall folded conformation and secondary structure. The midpoint values of GdnHCl mediated changes measured by inactivation; fluorescence and negative ellipticity were 0.48 M, 1.5 M and 1.9 M, respectively. The protein almost completely unfolded in 4.0 M GdnHCl but not at 90 A degrees C. The inactivation and unfolding were irreversible. At pH 2.0, the protein exhibited molten-globule like intermediate with rearranged secondary and tertiary structures and exposed hydrophobic amino acids on the surface. This species showed increased accessibility of Trp to the quenchers and got denatured with GdnHCl in a different manner. The insoluble aggregates of a thermally denatured protein could be detected only in the presence of 0.25-0.75 M GdnHCl.

}, keywords = {Aggregation, alpha-Mannosidase, ANS binding, Circular dichroism, fluorescence, GdnHCl, Hydrobicity, Thermal denaturation}, issn = {1053-0509}, doi = {10.1007/s10895-010-0625-1}, author = {Shashidhara, K. S. and Gaikwad, Sushama M.} } @article { ISI:000318142300022, title = {Solution and in silico studies on the recombinant lectin from Cicer arietinum seeds}, journal = {International Journal of Biological Macromolecules}, volume = {56}, year = {2013}, month = {MAY}, pages = {149-155}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The Cicer arietinum seed lectin was cloned and expressed in Escherichia coli and purified in active form. Conformational characterization of the recombinant lectin (rCAL) was performed using biophysical and bioinformatics tools. Thermal denaturation of rCAL caused rapid secondary structural rearrangements above 50 degrees C and transient exposure of hydrophobic residues at 55 degrees C, leading to aggregation. Treatment of rCAL with GdnHCl resulted in unfolding followed by dissociation of the dimer. The single tryptophan in rCAL present on the surface of the protein is surrounded by hydrophobic and acidic amino acids and exists as different conformers. The experimental observations correlated well with the structural information revealed from the homology model of rCAL. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {Aggregation, BL21-CodonPlus (DE3)-RIL cells, Cicer lectin, Homology model, Steady-state and time resolved fluorescence, Unfolding}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2013.02.015}, author = {Wakankar, Madhurima S. and Krishnasastry, Musti V. and Jaokar, Tulika M. and Patel, Krunal A. and Gaikwad, Sushama M.} } @article { ISI:000369200500019, title = {Functional and conformational transitions of mevalonate diphosphate decarboxylase from Bacopa monniera}, journal = {International Journal of Biological Macromolecules}, volume = {83}, year = {2016}, month = {FEB}, pages = {160-170}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Functional and conformational transitions of mevalonate diphosphate decarboxylase (MDD), a key enzyme of mevalonate pathway in isoprenoid biosynthesis, from Bacopa monniera (BmMDD), cloned and overexpressed in Escherichia coli were studied under thermal, chemical and pH-mediated denaturation conditions using fluorescence and Circular dichroism spectroscopy. Native BmMDD is a helix dominant structure with 45\% helix and 11\% sheets and possesses seven tryptophan residues with two residues exposed on surface, three residues partially exposed and two situated in the interior of the protein. Thermal denaturation of BmMDD causes rapid structural transitions at and above 40 degrees C and transient exposure of hydrophobic residues at 50 degrees C, leading to aggregation of the protein. An acid induced molten globule like structure was observed at pH 4, exhibiting altered but compact secondary structure, distorted tertiary structure and exposed hydrophobic residues. The molten globule displayed different response at higher temperature and similar response to chemical denaturation as compared to the native protein. The surface tryptophans have predominantly positively charged amino acids around them, as indicated by higher K-SV for IC as compared to that for CsCl. The native enzyme displayed two different lifetimes, vi (1.203 +/- 0.036 ns) and tau 2 (3.473 +/- 0.12 ns) indicating two populations of tryptophan. (C) 2015 Elsevier B.V. All rights reserved.

}, keywords = {Aggregation, CD spectroscopy, Fluorescence quenching, Mevalonate diphosphate decarboxylase, Unfolding}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2015.11.067}, author = {Shakeel, Abbassi and Patel, Krunal and Khan, Bashir Mohammad and Bhosale, Siddharth H. and Gaikwad, Sushama M.} } @article {46106, title = {Amphiphilic polypyridyl ruthenium complexes: synthesis, characterization and aggregation studies}, journal = {Polyhedron}, volume = {164}, year = {2019}, month = {MAY }, pages = {96-107}, type = {Article}, abstract = {

{Synthesis and characterization of five amphiphilic ruthenium(11) complexes of the type [Ru(Cn)(3)]center dot(PF6)(2) (Cn = 4,4{\textquoteright}-dialkyl-2,2{\textquoteright}-bipyridine

}, keywords = {2, 2 {\textquoteleft}-bipyridine, Aggregation, Amphiphilic ligand, Metallosurfactant, Ruthenium complexes}, issn = {0277-5387}, doi = {10.1016/j.poly.2019.02.035}, author = {Bhand, Sujit and Lande, Dipali N. and Pereira, Eulalia and Gejji, Shridhar P. and Weyhermueller, Thomas and Chakravarty, Debamitra and Puranik, Vedavati G. and Salunke-Gawali, Sunita} } @article {46615, title = {Effect of tert-alcohol functional imidazolium salts on oligomerization and fibrillization of amyloid beta (1-42) peptide}, journal = {Biophysical Chemistry}, volume = {267}, year = {2020}, month = {DEC}, pages = {106480}, type = {Article}, abstract = {

Imidazolium based IL{\textquoteright}s has gained vast interest in developing biological applications. Oligomerization and fibrillization of amyloid beta (1-42) peptide are mainly responsible for the extra-neuronal deposition of amyloid fibrils in neurodegenerative disorders like Alzheimer{\textquoteright}s disease (AD). Here, we report an effect of tert-BuOH-functional imidazolium ILs on oligomerization and fibrillization of amyloid beta (1-42) Peptide in vitro. In this study, a series of these [alkyl-(t)OHim][OMs] ILs with methyl sulphonate counter anion by varying alkyl chains were used. Among the seven protic ILs, four showed strong binding and inhibition activity for the formation of amyloid beta (1-42) aggregation by using Thioflavin T fluorescence binding assay. The secondary structural analysis of the peptide, pre-incubated with active ILs shows the loss of ordered beta-sheet amyloid structure. The longer alkyl chain ILs showed that an increased in amyloid binding and hence an inhibition effect on amyloid aggregation was enhanced. Thus, we propose that ILs could be presented as potential candidates for therapeutic intervention against Alzheimer{\textquoteright}s disease (AD).

}, keywords = {Aggregation, Amyloid beta (1-42) peptide, Biofilm inhibitor, Imidazolium ionic liquid}, issn = {0301-4622}, doi = {10.1016/j.bpc.2020.106480}, author = {Said, Madhukar S. and Navale, Govinda R. and Yadav, Ashok and Khonde, Nilesh and Shinde, Sandip S. and Jha, Anjali} } @article {46759, title = {Transition metal nickel prevents Tau aggregation in Alzheimer{\textquoteright}s disease}, journal = {International Journal of Biological Macromolecules}, volume = {156}, year = {2020}, month = {AUG }, pages = {1359-1365}, type = {Article}, abstract = {

Alzheimer{\textquoteright}s disease is the leading cause of dementia, effecting majority of aged people worldwide. The multifaceted effectors of Alzheimer{\textquoteright}s disease primarily include Tau, amyloid-beta along with hyper activation of kinases, oxidative stress and mutations etc., makes it challenging to design therapeutics. Tau is a microtubule-associating protein, which is subjected to cellular stress resulting in the formation of neurofibrillary tangles, leading to loss of affinity for microtubules. This causes loss of microtubule stability and in turn alters axonal integrity. In the present work, emphasis towards understanding interaction of nickel with Tau was made. Metals such as iron, zinc, copper and lead etc., are known to modulate Tau conformation and enhance its aggregation. Our results showed the deliverance of Tau aggregation by nickel and its synthetic morpholine conjugate. Nickel prevents aggregation by inducing degradation of Tau as evidenced by SDS-PAGE and TEM. Nickel and the synthetic conjugate being non toxic to neuro2a cells and prevent Tau aggregation, might direct these complexes to overcome AD. (C) 2019 Published by Elsevier B.V.

}, keywords = {Aggregation, Alzheimer{\textquoteright}s disease, metals, Morpholine, Nickel chloride, Tau}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2019.11.176}, author = {Gorantla, Nalini Vijay and Das, Rashmi and Balaraman, Ekambaram and Chinnathambi, Subashchandrabose} } @article {47364, title = {Methylation as a key regulator of Tau aggregation and neuronal health in Alzheimer{\textquoteright}s disease}, journal = {Cell Communication and Signaling}, volume = {19}, year = {2021}, month = {MAY }, pages = {51}, type = {Review}, abstract = {

Neurodegenerative diseases like Alzheimer{\textquoteright}s, Parkinson{\textquoteright}s and Huntington{\textquoteright}s disease involves abnormal aggregation and accumulation of toxic proteins aggregates. Post-translational modifications (PTMs) of the causative proteins play an important role in the etiology of disease as they could either slow down or accelerate the disease progression. Alzheimer disease is associated with the aggregation and accumulation of two major protein aggregates-intracellular neurofibrillary tangles made up of microtubule-associated protein Tau and extracellular Amyloid-beta plaques. Post-translational modifications are important for the regulation of Tau{\textquoteleft}s function but an imbalance in PTMs may lead to abnormal Tau function and aggregation. Tau methylation is one of the important PTM of Tau in its physiological state. However, the methylation signature on Tau lysine changes once it acquires pathological aggregated form. Tau methylation can compete with other PTMs such as acetylation and ubiquitination. The state of PTM at these sites determines the fate of Tau protein in terms of its function and stability. The global methylation in neurons, microglia and astrocytes are involved in multiple cellular functions involving their role in epigenetic regulation of gene expression via DNA methylation. Here, we have discussed the effect of methylation on Tau function in a site-specific manner and their cross-talk with other lysine modifications. We have also elaborated the role of methylation in epigenetic aspects and neurodegenerative conditions associated with the imbalance in methylation metabolism affecting global methylation state of cells.

}, keywords = {Aggregation, Epigenetics, methylation, Methyltransferases, post-translational modifications, Tau}, doi = {10.1186/s12964-021-00732-z}, author = {Balmik, Abhishek Ankur and Chinnathambi, Subashchandrabose} } @article {48474, title = {Design and synthesis of piano-stool ruthenium(II) complexes and their studies on the inhibition of amyloid ? (1-42) peptide aggregation}, journal = {International Journal of Biological Macromolecules}, volume = {239}, year = {2023}, month = {JUN }, pages = {124197}, type = {Article}, abstract = {

Misfolding , protein aggregation have been linked to numerous human neurodegenerative disorders such as Alzheimer{\textquoteright}s, prion , Parkinson{\textquoteright}s diseases. Ruthenium (Ru) complexes have received considerable attention in studying protein aggregation due to their interesting photophysical and photo properties. In this study, we have synthesized the novel Ru complexes ([Ru(p-cymene)Cl(L-1)][PF6](Ru-1), and [Ru(p-cymene)Cl(L-2)][PF6](Ru-2)) and investigated their inhibitory activity against the bovine serum albumin (BSA) aggregation and the A beta 1-42 peptides amyloid formation. Several spectroscopic methods were used to characterize these complexes, and the molecular structure of the complex was determined by X-ray crystallography. Amyloid aggregation and inhi-bition activities were examined using the Thioflavin-T (ThT) assay, and the secondary structures of the protein were analyzed by circular dichroism (CD) spectroscopy and transmission electron microscopy (TEM). The cell viability assay was carried out on the neuroblastoma cell line, revealing that the complex Ru-2 showed better protective effects against A beta 1-42 peptide toxicity on neuro-2a cells than the complex Ru-1. Molecular docking studies elucidate the binding sites and interactions between the Ru-complexes and A beta 1-42 peptides. The exper-imental studies revealed that these complexes significantly inhibited the BSA aggregation and A beta 1-42 amyloid fibril formation at 1:3 and 1:1 molar concentrations, respectively. Antioxidant assays demonstrated that these complexes act as antioxidants, protecting from amyloid-induced oxidative stress. Molecular docking studies with the monomeric A beta 1-42 (PDB: 1IYT) show hydrophobic interaction, and both complexes bind preferably in the central region of the peptide and coordinate with two binding sites of the peptide. Hence, we suggest that the Ru-based complexes could be applied as a potential agent in metallopharmaceutical research against Alzheimer{\textquoteright}s disease.

}, keywords = {Aggregation, Amyloid ?(1-42) peptide, DFT computation, Fibrillization, Molecular docking, Ruthenium complexes}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2023.124197}, author = {Singh, Sain and Navale, Govinda R. and Agrawal, Sonia and Singh, Haobam Kisan and Singla, Labhini and Sarkar, Dhiman and Sarma, Manabendra and Choudhury, Anghuman Roy and Ghosh, Kaushik} }