Monitoring pH-dependent conformational changes in aqueous solutions of poly(methacrylic acid)-b-polydimethylsiloxane copolymer based on fluorescence spectra of pyrene and 1,3-bis(1-pyrenyl)propane

The methodology of polarization time-resolved fluorometry and interpretation of its results are outlined at a general level, and the measurement on and use of facilities of the Edinburgh Instruments Model 299T apparatus are discussed in detail. The dynamics of conformational changes in chains of poly(methacrylic acid) containing covalently bonded dansyl labels are studied in aqueous solutions at various pH. It is shown that at pH > 6, the shorter effective rational correlation time τr < 2 ns corresponds to the rotation of the free dansyl label about bonds by which it is attached to the polymeric chain; at pH < 4 the longer effective rational correlation time τr = 20-26 ns corresponds to the rotation of the compact spherical formation constituted by a part of the collapsed polymeric chain in which the label is fixed and whose relative molecular mass is approx. 15 000-20 000.

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pH-Dependent Fluorescence Spectra, Lifetimes, and Quantum Yields of Firefly-Luciferin Aqueous Solutions Studied by Selective-Excitation Fluorescence Spectroscopy

Japanese Journal of Applied Physics ◽

10.1143/jjap.49.117002 ◽

2010 ◽

Vol 49 (11) ◽

pp. 117002 ◽

Cited By ~ 20

Author(s):

Yoriko Ando ◽

Hidefumi Akiyama

Keyword(s):

Fluorescence Spectroscopy ◽

Aqueous Solutions ◽

Fluorescence Spectra ◽

Selective Excitation ◽

Quantum Yields ◽

Firefly Luciferin ◽

Ph Dependent

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Fluorescence and FTIR Studies on the pH-Dependent Conformational Change of Poly(methacrylic acid) in Aqueous Solutions

Bulletin of the Chemical Society of Japan ◽

10.1246/bcsj.72.1233 ◽

1999 ◽

Vol 72 (6) ◽

pp. 1233-1238 ◽

Cited By ~ 10

Author(s):

Kenichi Nakashima ◽

Yoshinori Fujimoto ◽

Takayuki Anzai ◽

Jian Dong ◽

Hidetoshi Sato ◽

...

Keyword(s):

Aqueous Solutions ◽

Conformational Change ◽

Methacrylic Acid ◽

Ftir Studies ◽

Ph Dependent

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The X-Ray Crystallographic Structure of the Human Neonatal Fc Receptor at Acidic pH Gives Insights into pH-Dependent Conformational Changes

Protein and Peptide Letters ◽

10.2174/0929866523666160404125850 ◽

2016 ◽

Vol 23 (6) ◽

pp. 525-529 ◽

Cited By ~ 2

Author(s):

Mohammed Taha ◽

Sally E. Ward ◽

Hyun-Joo Nam

Keyword(s):

Conformational Changes ◽

Fc Receptor ◽

Crystallographic Structure ◽

Acidic Ph ◽

Neonatal Fc Receptor ◽

X Ray ◽

Ph Dependent

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pH-Dependent Thermal Stability of Vibrio cholerae L-asparaginase

Protein and Peptide Letters ◽

10.2174/0929866526666190617092944 ◽

2019 ◽

Vol 26 (10) ◽

pp. 743-750 ◽

Cited By ~ 1

Author(s):

Remya Radha ◽

Sathyanarayana N. Gummadi

Keyword(s):

Vibrio Cholerae ◽

Conformational Changes ◽

Kinetic Studies ◽

Structural Features ◽

Structure Stability ◽

Kcal Mole ◽

Scanning Calorimetry ◽

Wide Range ◽

Ph Dependent ◽

Ph Range

Background:pH is one of the decisive macromolecular properties of proteins that significantly affects enzyme structure, stability and reaction rate. Change in pH may protonate or deprotonate the side group of aminoacid residues in the protein, thereby resulting in changes in chemical and structural features. Hence studies on the kinetics of enzyme deactivation by pH are important for assessing the bio-functionality of industrial enzymes. L-asparaginase is one such important enzyme that has potent applications in cancer therapy and food industry.Objective:The objective of the study is to understand and analyze the influence of pH on deactivation and stability of Vibrio cholerae L-asparaginase.Methods:Kinetic studies were conducted to analyze the effect of pH on stability and deactivation of Vibrio cholerae L-asparaginase. Circular Dichroism (CD) and Differential Scanning Calorimetry (DSC) studies have been carried out to understand the pH-dependent conformational changes in the secondary structure of V. cholerae L-asparaginase.Results:The enzyme was found to be least stable at extreme acidic conditions (pH< 4.5) and exhibited a gradual increase in melting temperature from 40 to 81 °C within pH range of 4.0 to 7.0. Thermodynamic properties of protein were estimated and at pH 7.0 the protein exhibited ΔG37of 26.31 kcal mole-1, ΔH of 204.27 kcal mole-1 and ΔS of 574.06 cal mole-1 K-1.Conclusion:The stability and thermodynamic analysis revealed that V. cholerae L-asparaginase was highly stable over a wide range of pH, with the highest stability in the pH range of 5.0–7.0.

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Correlation of membrane protein conformational and functional dynamics

Nature Communications ◽

10.1038/s41467-021-24660-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Raghavendar Reddy Sanganna Gari ◽

Joel José Montalvo‐Acosta ◽

George R. Heath ◽

Yining Jiang ◽

Xiaolong Gao ◽

...

Keyword(s):

Membrane Protein ◽

Conformational Changes ◽

Single Channel ◽

Conformational Dynamics ◽

Md Simulations ◽

High Temporal Resolution ◽

Dependent Manner ◽

Functional Dynamics ◽

Ph Dependent ◽

Open States

AbstractConformational changes in ion channels lead to gating of an ion-conductive pore. Ion flux has been measured with high temporal resolution by single-channel electrophysiology for decades. However, correlation between functional and conformational dynamics remained difficult, lacking experimental techniques to monitor sub-millisecond conformational changes. Here, we use the outer membrane protein G (OmpG) as a model system where loop-6 opens and closes the β-barrel pore like a lid in a pH-dependent manner. Functionally, single-channel electrophysiology shows that while closed states are favored at acidic pH and open states are favored at physiological pH, both states coexist and rapidly interchange in all conditions. Using HS-AFM height spectroscopy (HS-AFM-HS), we monitor sub-millisecond loop-6 conformational dynamics, and compare them to the functional dynamics from single-channel recordings, while MD simulations provide atomistic details and energy landscapes of the pH-dependent loop-6 fluctuations. HS-AFM-HS offers new opportunities to analyze conformational dynamics at timescales of domain and loop fluctuations.

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