1
|
Baluchi A, Homaei A. Immobilization of l-asparaginase on chitosan nanoparticles for the purpose of long-term application. Int J Biol Macromol 2024; 257:128655. [PMID: 38065449 DOI: 10.1016/j.ijbiomac.2023.128655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 11/26/2023] [Accepted: 12/05/2023] [Indexed: 01/26/2024]
Abstract
Asparaginase holds significant commercial value as an enzyme in the food and pharmaceutical industries. This study examined the optimum and practical use of the l-asparaginase derived from Pseudomonas aeruginosa HR03. Specifically, the study focused on the effectiveness of the stabilized enzyme when applied to chitosan nanoparticles. The structure, size, and morphology of chitosan nanoparticles were evaluated in relation to the immobilization procedure. This assessment involved the use of several analytical techniques, including FT-IR, DLS, SEM, TEM, and EDS analysis. Subsequently, the durability of the enzyme that has been stabilized was assessed by evaluating its effectiveness under extreme temperatures of 60 and 70 °C, as well as at pH values of 3 and 12. The findings indicate that incorporating chitosan nanoparticles led to enhanced immobilization of the l-asparaginase enzyme. This improvement was observed in terms of long-term stability, stability under crucial temperature and pH conditions, as well as thermal stability. In addition, the optimum temperature increased from 40 to 50 °C, and the optimum pH increased from 8 to 9. Enzyme immobilization led to an increase in Km and a decrease in kcat compared to its free counterpart. Because of its enhanced long-term stability, l-asparaginase immobilization on chitosan nanoparticles may be a potential choice for use in industries that rely on l-asparaginase enzymes, particularly the pharmaceutical and food industries.
Collapse
Affiliation(s)
- Ayeshe Baluchi
- Department of Marine Biology, Faculty of Marine Science and Technology, University of Hormozgan, Bandarabbas, Iran
| | - Ahmad Homaei
- Department of Marine Biology, Faculty of Marine Science and Technology, University of Hormozgan, Bandarabbas, Iran.
| |
Collapse
|
2
|
Sargautis D, Kince T. Effect of Enzymatic Pre-Treatment on Oat Flakes Protein Recovery and Properties. Foods 2023; 12:foods12050965. [PMID: 36900482 PMCID: PMC10001348 DOI: 10.3390/foods12050965] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 03/02/2023] Open
Abstract
Oats are considered an exceptional source of high-quality protein. Protein isolation methods define their nutritional value and further applicability in food systems. The aim of this study was to recover the oat protein using a wet-fractioning method and investigate the protein functional properties and nutritional values among the processing streams. The oat protein was concentrated through enzymatic extraction, eliminating starch and non-starch polysaccharides (NSP), treating oat flakes with hydrolases, and reaching protein concentrations of up to about 86% in dry matter. The increased ionic strength from adding sodium chloride (NaCl) improved protein aggregation and resulted in increased protein recovery. Ionic changes improved protein recovery in provided methods by up to 24.8 % by weight. Amino acid (AA) profiles were determined in the obtained samples, and protein quality was compared with the required pattern of indispensable amino acids. Furthermore, functional properties of the oat protein, such as solubility, foamability, and liquid holding capacity, were investigated. The solubility of the oat protein was below 7 %; foamability averaged below 8%. The water and oil-holding reached a ratio of up to 3.0 and 2.1 for water and oil, respectively. Our findings suggest that oat protein could be a potential ingredient for food industries requiring a protein of high purity and nutritional value.
Collapse
|
3
|
Conformational Stability and Denaturation Processes of Proteins Investigated by Electrophoresis under Extreme Conditions. Molecules 2022; 27:molecules27206861. [PMID: 36296453 PMCID: PMC9610776 DOI: 10.3390/molecules27206861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 10/10/2022] [Accepted: 10/10/2022] [Indexed: 11/17/2022] Open
Abstract
The functional structure of proteins results from marginally stable folded conformations. Reversible unfolding, irreversible denaturation, and deterioration can be caused by chemical and physical agents due to changes in the physicochemical conditions of pH, ionic strength, temperature, pressure, and electric field or due to the presence of a cosolvent that perturbs the delicate balance between stabilizing and destabilizing interactions and eventually induces chemical modifications. For most proteins, denaturation is a complex process involving transient intermediates in several reversible and eventually irreversible steps. Knowledge of protein stability and denaturation processes is mandatory for the development of enzymes as industrial catalysts, biopharmaceuticals, analytical and medical bioreagents, and safe industrial food. Electrophoresis techniques operating under extreme conditions are convenient tools for analyzing unfolding transitions, trapping transient intermediates, and gaining insight into the mechanisms of denaturation processes. Moreover, quantitative analysis of electrophoretic mobility transition curves allows the estimation of the conformational stability of proteins. These approaches include polyacrylamide gel electrophoresis and capillary zone electrophoresis under cold, heat, and hydrostatic pressure and in the presence of non-ionic denaturing agents or stabilizers such as polyols and heavy water. Lastly, after exposure to extremes of physical conditions, electrophoresis under standard conditions provides information on irreversible processes, slow conformational drifts, and slow renaturation processes. The impressive developments of enzyme technology with multiple applications in fine chemistry, biopharmaceutics, and nanomedicine prompted us to revisit the potentialities of these electrophoretic approaches. This feature review is illustrated with published and unpublished results obtained by the authors on cholinesterases and paraoxonase, two physiologically and toxicologically important enzymes.
Collapse
|
4
|
Zhou L, Chen F, Liu K, Zhu T, Jiang L. Combination of Alcalase 2.4 L and CaCl 2 for aqueous extraction of peanut oil. J Food Sci 2020; 85:1772-1780. [PMID: 32484970 DOI: 10.1111/1750-3841.15158] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 04/04/2020] [Accepted: 04/08/2020] [Indexed: 11/28/2022]
Abstract
The combined application of CaCl2 and Alcalase 2.4 L to the aqueous extraction process of peanuts was evaluated as a method to destabilize the oil body (OB) emulsion and improve the oil yield. After adding 5 mM CaCl2 , the oil yield was reached to 92.0% which was similar with that obtained using Alcalase 2.4 L alone, and the required enzyme loading was decreased by approximately 60 times. In addition, the demulsification mechanism during aqueous extraction process was also investigated. Particle size and zeta-potential measurements indicated that the stability of the peanut OB emulsion dramatically decreased when CaCl2 was added. Under these conditions, the demulsification of Alcalase 2.4 L performed was more efficiently. SDS-PAGE results showed that adding CaCl2 changed the subunit structure of the peanut OB interface proteins and promoted the cross-linking among the arachin Ara h3 isoforms, resulting in unstable emulsions.
Collapse
Affiliation(s)
- Longzheng Zhou
- College of Food Science and Technology, Henan University of Technology, Zhengzhou, 450001, China
| | - Fusheng Chen
- College of Food Science and Technology, Henan University of Technology, Zhengzhou, 450001, China
| | - Kunlun Liu
- College of Food Science and Technology, Henan University of Technology, Zhengzhou, 450001, China
| | - Tingwei Zhu
- College of Food Science and Technology, Henan University of Technology, Zhengzhou, 450001, China
| | - Lianzhou Jiang
- College of Food Science, Northeast Agricultural University, Harbin, 150030, China
| |
Collapse
|
5
|
Volumetric studies of solvation of carboxylic acids in aqueous, carbon tetrachloride, methanolic and methanolic-urea binary solutions at 298.15 K. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.112658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
6
|
Custodio KS, Claudio GC, Nellas RB. Structural Dynamics of Neighboring Water Molecules of N-Isopropylacrylamide Pentamer. ACS OMEGA 2020; 5:1408-1413. [PMID: 32010812 PMCID: PMC6990436 DOI: 10.1021/acsomega.9b02898] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 12/30/2019] [Indexed: 06/10/2023]
Abstract
Poly(N-isopropylacrylamide) (PNIPAM) is a popular polymer widely used in smart hydrogel synthesis due to its thermo-responsive behavior in aqueous medium. Aqueous PNIPAM hydrogels can reversibly swell and collapse below and above their lower critical solution temperature (LCST), respectively. The present work used molecular dynamics simulations to explore the behavior of water molecules surrounding the side chains of a NIPAM pentamer in response to temperature changes (273-353 K range) near its experimental LCST (305 K). Results suggest a strong inverse correlation of temperature with water density and hydrophobic hydration character of the first coordination shell around the isopropyl groups. Integrity of the first and second coordination shells is further characterized by polygon ring analysis. Predominant occurrence of pentagons suggests clathrate-like behavior of both shells at lower temperatures. This predominance is eventually overtaken by 4-membered rings as temperature is increased beyond 303 and 293 K for the first and second coordination shells, respectively, losing their clathrate-like property. It is surmised that this temperature-dependent stability of the coordination shells is one of the important factors that controls the reversible swell-collapse mechanism of PNIPAM hydrogels.
Collapse
Affiliation(s)
| | | | - Ricky B. Nellas
- E-mail: . Phone: +63 2 981 8500 loc 3652. Fax: +63 2
920 5432
| |
Collapse
|
7
|
Preferential solvation of lysozyme in dimethyl sulfoxide/water binary mixture probed by terahertz spectroscopy. Biophys Chem 2016; 216:31-36. [DOI: 10.1016/j.bpc.2016.06.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 06/14/2016] [Accepted: 06/14/2016] [Indexed: 11/21/2022]
|
8
|
Sen S, Voorheis HP. Protein folding: understanding the role of water and the low Reynolds number environment as the peptide chain emerges from the ribosome and folds. J Theor Biol 2014; 363:169-87. [PMID: 25152217 DOI: 10.1016/j.jtbi.2014.07.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 06/20/2014] [Accepted: 07/25/2014] [Indexed: 11/19/2022]
Abstract
The mechanism of protein folding during early stages of the process has three determinants. First, moving water molecules obey the rules of low Reynolds number physics without an inertial component. Molecular movement is instantaneous and size insensitive. Proteins emerging from the ribosome move and rotate without an external force if they change shape, forming and propagating helical structures that increases translocational efficiency. Forward motion ceases when the shape change or propelling force ceases. Second, application of quantum field theory to water structure predicts the spontaneous formation of low density coherent units of fixed size that expel dissolved atmospheric gases. Structured water layers with both coherent and non-coherent domains, form a sheath around the new protein. The surface of exposed hydrophobic amino acids is protected from water contact by small nanobubbles of dissolved atmospheric gases, 5 or 6 molecules on average, that vibrate, attracting even widely separated resonating nanobubbles. This force results from quantum effects, appearing only when the system is within and interacts with an oscillating electromagnetic field. The newly recognized quantum force sharply bends the peptide and is part of a dynamic field determining the pathway of protein folding. Third, the force initiating the tertiary folding of proteins arises from twists at the position of each hydrophobic amino acid, that minimizes surface exposure of the hydrophobic amino acids and propagates along the protein. When the total bend reaches 360°, the leading segment of water sheath intersects the trailing segment. This steric self-intersection expels water from overlapping segments of the sheath and by Newton׳s second law moves the polypeptide chain in an opposite direction. Consequently, with very few exceptions that we enumerate and discuss, tertiary structures are absent from proteins without hydrophobic amino acids, which control the early stages of protein folding and the overall shape of protein. Consequently, proteins only adopt a limited number of forms. The formation of quaternary structures is not necessarily prevented by the absence of hydrophobic amino acids.
Collapse
Affiliation(s)
| | - H Paul Voorheis
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland
| |
Collapse
|
9
|
Mehta A, Rao JR, Fathima NN. Can green solvents be alternatives for thermal stabilization of collagen? Int J Biol Macromol 2014; 69:361-8. [DOI: 10.1016/j.ijbiomac.2014.05.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 04/01/2014] [Accepted: 05/08/2014] [Indexed: 10/25/2022]
|
10
|
Jain R, Sharma D, Kumar R. Effects of alcohols on the stability and low-frequency local motions that control the slow changes in structural dynamics of ferrocytochrome c. J Biochem 2013; 154:341-54. [DOI: 10.1093/jb/mvt059] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
11
|
Sashi P, Yasin UM, Bhuyan AK. Unfolding action of alcohols on a highly negatively charged state of cytochrome C. Biochemistry 2012; 51:3273-83. [PMID: 22439732 DOI: 10.1021/bi201716r] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
It is well-known that hydrophobic effect play a major role in alcohol-protein interactions leading to structure unfolding. Studies with extremely alkaline cytochrome c (U(B) state, pH 13) in the presence of the first four alkyl alcohols suggests that the hydrophobic effect persistently overrides even though the protein carries a net charge of -17 under these conditions. Equilibrium unfolding of the U(B) state is accompanied by an unusual expansion of the chain involving an intermediate, I(alc), from which water is preferentially excluded, the extent of water exclusion being greater with the hydrocarbon content of the alcohol. The mobility and environmental averaging of side chains in the I(alc) state are generally constrained relative to those in the U(B) state. A few nuclear magnetic resonance-detected tertiary interactions are also found in the I(alc) state. The fact that the I(alc) state populates at low concentrations of methanol and ethanol and the fact that the extent of chain expansion in this state approaches that of the U(B) state indicate a definite influence of electrostatic repulsion severed by the low dielectric of the water/alcohol mixture. Interestingly, the U(B) ⇌ I(alc) segment of the U(B) ⇌ I(alc) ⇌ U equilibrium, where U is the unfolded state, accounts for roughly 85% of the total number of water molecules preferentially excluded in unfolding. Stopped-flow refolding results report on a submillisecond hydrophobic collapse during which almost the entire buried surface area associated with the U(B) state is recovered, suggesting the overwhelming influence of hydrophobic interaction over electrostatic repulsions.
Collapse
Affiliation(s)
- Pulikallu Sashi
- School of Chemistry, University of Hyderabad, Hyderabad 500 046, India
| | | | | |
Collapse
|
12
|
Yin SW, Tang CH, Wen QB, Yang XQ. Conformational and thermal properties of phaseolin, the major storage protein of red kidney bean (Phaseolus vulgaris L.). JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2011; 91:94-99. [PMID: 20815040 DOI: 10.1002/jsfa.4155] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2010] [Revised: 07/29/2010] [Accepted: 07/30/2010] [Indexed: 05/29/2023]
Abstract
BACKGROUND A previous study of various functional and physicochemical properties of phaseolin indicated good potential of phaseolin for application in food formulations in view of its excellent functional properties. The aim of the present study was to explore the conformational and thermal properties of phaseolin in the presence of protein structural perturbants by intrinsic fluorescence emission spectroscopy and differential scanning calorimetry. Raman spectroscopy was also used to characterise the secondary structures of phaseolin. RESULTS The Raman spectrum of phaseolin indicated that β-sheets and random coils were the major secondary structures. Intrinsic fluorescence emission spectroscopy confirmed the structural peculiarity and compactness of phaseolin, as evidenced by the absence of any shift in emission maximum (λ(max)) in the presence of structural perturbants such as sodium dodecyl sulfate (SDS), guanidine hydrochloride, urea and dithiothreitol (DTT). Increasing NaCl concentration enhanced the thermal stability of phaseolin. Addition of chaotropic salts (1 mol L(-1)) caused progressive decreases in thermal stability following the lyotropic series of anions. Decreases in thermal denaturation temperature (T(d)) and enthalpy change (ΔH) were observed in the presence of protein perturbants such as SDS, urea and ethylene glycol, indicating partial denaturation and a decrease in thermal stability. DTT and N-ethylmaleimide had little effect on the thermal properties of phaseolin, confirming that phaseolin, a 7S globulin, is devoid of inter-polypeptide disulfide bonds. CONCLUSION The data presented here demonstrate the contributions of hydrophobic and electrostatic interactions and hydrogen bonding to the conformational stability of phaseolin.
Collapse
Affiliation(s)
- Shou-Wei Yin
- Department of Food Science and Technology, South China University of Technology, Guangzhou, China
| | | | | | | |
Collapse
|
13
|
Yin SW, Tang CH, Yang XQ, Wen QB. Conformational study of red kidney bean (Phaseolus vulgaris L.) protein isolate (KPI) by tryptophan fluorescence and differential scanning calorimetry. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:241-248. [PMID: 21126074 DOI: 10.1021/jf1027608] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Fluorescence and differential scanning calorimetry (DSC) were used to study changes in the conformation of red kidney bean (Phaseolus vulgaris L.) protein isolate (KPI) under various environmental conditions. The possible relationship between fluorescence data and DSC characteristics was also discussed. Tryptophan fluorescence and fluorescence quenching analyses indicated that the tryptophan residues in KPI, exhibiting multiple fluorophores with different accessibilities to acrylamide, are largely buried in the hydrophobic core of the protein matrix, with positively charged side chains close to at least some of the tryptophan residues. GdnHCl was more effective than urea and SDS in denaturing KPI. SDS and urea caused variable red shifts, 2-5 nm, in the emission λ(max), suggesting the conformational compactness of KPI. The result was further supported by DSC characteristics that a discernible endothermic peak was still detected up to 8 M urea or 30 mM SDS, also evidenced by the absence of any shift in emission maximum (λ(max)) at different pH conditions. Marked decreases in T(d) and enthalpy (ΔH) were observed at extreme alkaline and/or acidic pH, whereas the presence of NaCl resulted in higher T(d) and ΔH, along with greater cooperativity of the transition. Decreases in T(d) and ΔH were observed in the presence of protein perturbants, for example, SDS and urea, indicating partial denaturation and decrease in thermal stability. Dithiothreitol and N-ethylmaleimide have a slight effect on the thermal properties of KPI. Interestingly, a close linear relationship between the T(d) (or ΔH) and the λ(max) was observed for KPI in the presence of 0-6 M urea.
Collapse
Affiliation(s)
- Shou-Wei Yin
- Department of Food Science and Technology, South China University of Technology, Guangzhou, People's Republic of China.
| | | | | | | |
Collapse
|
14
|
Abstract
To understand the physical state of water in hydrating biological tissues, thermodynamic properties of water in cotyledons of pea and soybean with moisture contents ranging from 0.01 g H(2)O/g dw to 1.0 g H(2)O/g dw were studied using differential scanning calorimetry. The heat capacity of the tissues increased abruptly at moisture contents above 0.08 and 0.12 g H(2)O/g dw for soybean and pea cotyledons, respectively. Melting transitions of water were observed at moisture contents >0.23 and 0.26 g H(2)O/g dw for soybean and pea. However, freezing of water was not observed unless moisture contents exceeded 0.33-0.35 g H(2)O/g dw. In both seed tissues, the temperatures of the freezing and melting varied with moisture content and showed hysterisis. The energy of the transition also varied with moisture content and was similar to the heats of fusion and crystallization of pure water only at moisture contents >0.54 and 0.58 gH(2)O/g dw for soybean and pea seeds, respectively. The thermal properties of water change distinctly as seed moisture content changes: at least five states or water can be identified.
Collapse
|
15
|
|
16
|
Kurhe DN, Dagade DH, Jadhav JP, Govindwar SP, Patil KJ. Studies of Enthalpy−Entropy Compensation, Partial Entropies, and Kirkwood−Buff Integrals for Aqueous Solutions of Glycine, l-Leucine, and Glycylglycine at 298.15 K. J Phys Chem B 2009; 113:16612-21. [DOI: 10.1021/jp9078585] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Deepti N. Kurhe
- Department of Biochemistry, Shivaji University, Kolhapur 416004, India, Department of Chemistry, Shivaji University, Kolhapur 416004, India
| | - Dilip H. Dagade
- Department of Biochemistry, Shivaji University, Kolhapur 416004, India, Department of Chemistry, Shivaji University, Kolhapur 416004, India
| | - Jyoti P. Jadhav
- Department of Biochemistry, Shivaji University, Kolhapur 416004, India, Department of Chemistry, Shivaji University, Kolhapur 416004, India
| | - Sanjay P. Govindwar
- Department of Biochemistry, Shivaji University, Kolhapur 416004, India, Department of Chemistry, Shivaji University, Kolhapur 416004, India
| | - Kesharsingh J. Patil
- Department of Biochemistry, Shivaji University, Kolhapur 416004, India, Department of Chemistry, Shivaji University, Kolhapur 416004, India
| |
Collapse
|
17
|
|
18
|
Studies of densities, apparent molal volume, viscosities, surface tension and free energies of activation for interactions of praseodymium Sal2en complex with dimethylsulphoxide. J Mol Liq 2009. [DOI: 10.1016/j.molliq.2009.04.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
19
|
|
20
|
ẐZEROVNIK EVA, LAPANJE SAVO. Thermodynamic studies of the interactions of alkylureas with glycine, diglycine, and triglycine. ACTA ACUST UNITED AC 2009. [DOI: 10.1111/j.1399-3011.1987.tb03305.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
21
|
Effect of salt addition on the thermal behavior of proteins of bovine meat from Argentina. Meat Sci 2008; 79:549-56. [DOI: 10.1016/j.meatsci.2007.12.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
22
|
Abstract
Samples of methionine carrying a chiral CHDT-group have been prepared from and degraded chemically to chiral acetic acid. With this powerful tool inversion mechanisms were detected for the methylations on sulphur, oxygen and carbon atoms in the biosynthesis of methionine, loganin and cyanocobalamin, respectively. Chirality of the methyl group of methionine is retained during formation of the C-24 methyl group in ergosterol biosynthesis. A stereochemical scheme for the unusual course of this reaction is presented and the current stage of experiments aimed at its verification is discussed.
Collapse
|
23
|
Modeling structure and flexibility of Candida antarctica lipase B in organic solvents. BMC STRUCTURAL BIOLOGY 2008; 8:9. [PMID: 18254946 PMCID: PMC2262892 DOI: 10.1186/1472-6807-8-9] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Accepted: 02/06/2008] [Indexed: 11/22/2022]
Abstract
Background The structure and flexibility of Candida antarctica lipase B in water and five different organic solvent models was investigated using multiple molecular dynamics simulations to describe the effect of solvents on structure and dynamics. Interactions of the solvents with the protein and the distribution of water molecules at the protein surface were examined. Results The simulated structure was independent of the solvent, and had a low deviation from the crystal structure. However, the hydrophilic surface of CALB in non-polar solvents decreased by 10% in comparison to water, while the hydrophobic surface is slightly increased by 1%. There is a large influence on the flexibility depending on the dielectric constant of the solvent, with a high flexibility in water and a low flexibility in organic solvents. With decreasing dielectric constant, the number of surface bound water molecules significantly increased and a spanning water network with an increasing size was formed. Conclusion The reduced flexibility of Candida antarctica lipase B in organic solvents is caused by a spanning water network resulting from less mobile and slowly exchanging water molecules at the protein-surface. The reduced flexibility of Candida antarctica lipase B in organic solvent is not only caused by the interactions between solvent-protein, but mainly by the formation of a spanning water network.
Collapse
|
24
|
Pierce V, Kang M, Aburi M, Weerasinghe S, Smith PE. Recent applications of Kirkwood-Buff theory to biological systems. Cell Biochem Biophys 2007; 50:1-22. [PMID: 18043873 PMCID: PMC2566781 DOI: 10.1007/s12013-007-9005-0] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2007] [Accepted: 11/02/2007] [Indexed: 12/01/2022]
Abstract
The effect of cosolvents on biomolecular equilibria has traditionally been rationalized using simple binding models. More recently, a renewed interest in the use of Kirkwood-Buff (KB) theory to analyze solution mixtures has provided new information on the effects of osmolytes and denaturants and their interactions with biomolecules. Here we review the status of KB theory as applied to biological systems. In particular, the existing models of denaturation are analyzed in terms of KB theory, and the use of KB theory to interpret computer simulation data for these systems is discussed.
Collapse
Affiliation(s)
- Veronica Pierce
- Department of Chemistry, 111 Willard Hall, Kansas State University, Manhattan, KS 66506-3701, USA
| | | | | | | | | |
Collapse
|
25
|
Terdale SS, Dagade DH, Patil KJ. Thermodynamic Studies of Drug−α-Cyclodextrin Interactions in Water at 298.15 K: Promazine Hydrochloride/Chlorpromazine Hydrochloride + α-Cyclodextrin + H2O Systems. J Phys Chem B 2007; 111:13645-52. [DOI: 10.1021/jp0754381] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Dilip H. Dagade
- Department of Chemistry, Shivaji University, Kolhapur − 416 004, India
| | | |
Collapse
|
26
|
Dagade DH, Shetake PK, Patil KJ. Thermodynamic Studies of Aqueous and CCl4 Solutions of 15-Crown-5 at 298.15 K: An Application of McMillan−Mayer and Kirkwood−Buff Theories of Solutions. J Phys Chem B 2007; 111:7610-9. [PMID: 17547449 DOI: 10.1021/jp071155x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The density and osmotic coefficient data for solutions of 15-crown-5 (15C5) in water and in CCl4 solvent systems at 298.15 K have been reported using techniques of densitometry and vapor pressure osmometry in the concentration range of 0.01-2 mol kg-1. The data are used to obtain apparent molar and partial molar volumes, activity coefficients of the components as a function of 15C5 concentration. Using the literature heat of dilution data for aqueous system, it has become possible to calculate entropy of mixing (DeltaS(mix)), excess entropy of solution (DeltaS(E)), and partial molar entropies of the components at different concentrations. The results of all these are compared to those obtained for aqueous 18-crown-6 solutions reported earlier. It has been observed that the partial molar volume of 15C5 goes through a minimum and that of water goes through a maximum at approximately 1.2 mol kg(-1) in aqueous solutions whereas the opposite is true in CCl4 medium but at approximately 0.5 mol kg(-1). The osmotic and activity coefficients of 15C5 and excess free energy change for solution exhibit distinct differences in the two solvent systems studied. These results have been explained in terms of hydrophobic hydration and interactions in aqueous solution while weak solvophobic association of 15C5 molecules in CCl4 solutions is proposed. The data are further subjected to analysis by applying McMillan-Mayer and Kirkwood-Buff theories of solutions. The analysis shows that osmotic second virial coefficient value for 15C5 is marginally less than that of 18C6 indicating that reduction in ring flexibility does not affect the energetics of the interactions much in aqueous solution while the same gets influenced much in nonpolar solvent CCl4.
Collapse
Affiliation(s)
- Dilip H Dagade
- Department of Chemistry, Shivaji University, Kolhapur 416 004, India.
| | | | | |
Collapse
|
27
|
Jolicoeur C. Thermodynamic flow methods in biochemistry: calorimetry, densimetry, and dilatometry. METHODS OF BIOCHEMICAL ANALYSIS 2006; 27:171-287. [PMID: 6455585 DOI: 10.1002/9780470110478.ch4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
|
28
|
Quantum chemical studies on the tautomerism of some potentially tautomeric aminoindazole derivatives. Struct Chem 2006. [DOI: 10.1007/s11224-006-9019-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
29
|
|
30
|
|
31
|
Ellepola SW, Choi SM, Ma CY. Conformational study of globulin from rice (Oryza sativa) seeds by Fourier-transform infrared spectroscopy. Int J Biol Macromol 2005; 37:12-20. [PMID: 16140371 DOI: 10.1016/j.ijbiomac.2005.07.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Revised: 07/25/2005] [Accepted: 07/25/2005] [Indexed: 10/25/2022]
Abstract
The conformation of rice globulin (10%, w/v, in deuterated phosphate buffer, pD 7.4) under the influence of pH, chaotropic salts, several protein structure perturbants and heat treatments was studied by Fourier-transform infrared (FTIR) spectroscopy. Rice globulin exhibited seven major bands in the region of 1700-1600 cm-1 and the spectrum suggests high alpha-helical content with large quantities of beta-sheet and beta-turn structures. Highly acidic and alkaline pH conditions induced changes in band intensity attributed to intermolecular beta-sheet structure (1681 and 1619 cm-1). Addition of chaotropic salts led to progressive changes in band intensity, following the lyotropic series of anions, whereas several protein structure perturbants caused shifts in band positions. Heating at increasing temperature led to progressive decreases in alpha-helical content and increases in random coil structures, suggesting protein denaturation. This was accompanied by intensity increases in the intermolecular beta-sheet transitions.
Collapse
|
32
|
Mehta R, Kundu A, Kishore N. 4-Chlorobutanol induces unusual reversible and irreversible thermal unfolding of ribonuclease A: thermodynamic, kinetic, and conformational characterization. Int J Biol Macromol 2004; 34:13-20. [PMID: 15178004 DOI: 10.1016/j.ijbiomac.2003.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2003] [Indexed: 10/26/2022]
Abstract
The thermal denaturation of ribonuclease A has been studied by differential scanning calorimetry in the presence of 4-chlorobutan-1-ol. The thermal transitions were observed to be reversible at pH 5.5 in the presence of low concentration (up to 50 mM) of the alcohol, irreversible in the intermediate (50 mM < c < mM) and again reversible in the presence of 250 mM and higher concentrations of 4-chlorobutan-1-ol. In the presence of 50 mM 4-chlorobutan-1-ol, ribonuclease A is present in two conformational states unfolding at different temperatures. The reversible thermal transitions have been fitted to a two-state native-to-denatured mechanism. Irreversible thermal transitions have been analyzed according to two-state irreversible native-to-denatured kinetic model. Using the irreversible model, rate constant as a function of temperature and energy of activation of the irreversible process have been calculated. Circular dichroism and fluorescence spectroscopic results corroborate the DSC observations and indicate a protein conformation with poorly defined tertiary structure and high content of secondary structure in the presence of 50 mM 4-chlorobutan-1-ol at a temperature corresponding to the second transition. Similar results have been observed at pH 3.9.
Collapse
Affiliation(s)
- Ranjana Mehta
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | | | | |
Collapse
|
33
|
|
34
|
Weerasinghe S, Smith PE. Cavity formation and preferential interactions in urea solutions: Dependence on urea aggregation. J Chem Phys 2003. [DOI: 10.1063/1.1557431] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
35
|
Marlow GE, Pettitt BM. Simulation of the bis-(penicillamine) enkephalin in ammonium chloride solution: a comparison with sodium chloride. Biopolymers 2003; 68:192-209. [PMID: 12548623 DOI: 10.1002/bip.10292] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In order to quantify specific ion effects, a simulation study of bis(penicllamine) enkephalin, also known as DPDPE, has been performed in aqueous ammonium chloride solution and has been compared to a previous simulation of DPDPE in aqueous sodium chloride solution. Global thermodynamics have been calculated for a model system and the solution environment around DPDPE has been characterized. Associations of ions with DPDPE have been investigated. The observed differences between sodium chloride solution and ammonium chloride solution suggest that individual cations affect the solvation and peptide binding properties of a given anion.
Collapse
Affiliation(s)
- Gail E Marlow
- Department of Chemistry, University of Houston, Houston, TX 77204-5003, USA
| | | |
Collapse
|
36
|
Li-Chan E, Ma CY. Thermal analysis of flaxseed (Linum usitatissimum) proteins by differential scanning calorimetry. Food Chem 2002. [DOI: 10.1016/s0308-8146(01)00365-x] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
37
|
|
38
|
Abstract
A simulation study of DPDPE in sodium chloride solution has been performed and compared with previous simulations using a different interaction potential for the ions. Both global thermodynamics as well as a characterization of association to DPDPE have been calculated. We show that the parameters used for the ions have a profound effect on the association to the peptide in 1M NaCl. The observed differences suggest that individual associations in these and previous simulations are sensitive to parameters.
Collapse
Affiliation(s)
- G E Marlow
- Department of Chemistry, University of Houston, Houston, TX 77204-5641, USA
| | | |
Collapse
|
39
|
Lefèvre T, Subirade M. Conformational rearrangement of beta-lactoglobulin upon interaction with an anionic membrane. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1549:37-50. [PMID: 11566367 DOI: 10.1016/s0167-4838(01)00242-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Interactions between beta-lactoglobulin (beta-lg) and dimyristoylphosphatidylglycerol (DMPG) bilayers were studied using one- and two-dimensional infrared spectroscopy above (pD 7.4) and below (pD 4.4) the protein's (beta-lg's) isoelectric point (pI=5.2). The aim of the study was threefold: (1) gain a better understanding of beta-lg-phospholipid interaction; (2) provide information relative to the structure of beta-lg as it interacts with membranes; (3) determine whether the conformational modifications of the protein in the presence of lipids are strictly caused by thermal effects or whether they are modulated by the chain-melting phase transition. At pD 7.4, the lipid thermotropism, the acyl-chain order, and the membrane interfacial region were essentially unaffected by the presence of beta-lg, whereas the protein amide I region showed dramatic alterations. The results suggested the predominance of beta-sheets and alpha-helix elements, with a lost of structural integrity. At pD 4.4, beta-lg induced an approximately 2 degrees C downshift of the transition temperature, whereas the conformational order of the lipid chain decreased in the gel phase and increased in the liquid-crystalline phase. The hydration state of the DMPG C==O groups increased in the liquid-crystalline phase. The conformation of beta-lg at pD 4.4 in the presence of DMPG showed similarities with that observed at pD 7.4, but an increase in the alpha-helix content and a reduced thermal stability were noticed. In contrast to the protein alone, beta-lg aggregates in the presence of DMPG at pD 4.4 above 50 degrees C. At both pD values, the charged surface of the membrane seemed to be the main factor for inducing protein conformational changes by altering the intramolecular interactions that stabilize the native structure. However, protein incorporation within the membrane seemed to be involved at pD 4.4. The two-dimensional analysis performed with spectra recorded upon heating showed that spectral intensity changes at pD 4.4 and 7.4 occurred at the same frequencies in the amide I' region. The heat-induced structural changes of beta-lg were not correlated with the conformational modifications of the phospholipids along the phase transition, indicating that the thermal behavior of the protein was not modulated by the lipid chain melting, but rather represented the heat-induced protein rearrangement in the presence of DMPG.
Collapse
Affiliation(s)
- T Lefèvre
- Centre de Recherches en Sciences et Technologie du Lait (STELA), Département d'Alimentation et de Nutrition, Faculté des Sciences de l'Agriculture et de l'Alimentation, Pavillon Paul Comtois, Université Laval, Sainte-Foy, QC, Canada G1K 7P4
| | | |
Collapse
|
40
|
|
41
|
Ma CY, Rout MK, Chan WM, Phillips DL. Raman spectroscopic study of oat globulin conformation. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2000; 48:1542-1547. [PMID: 10820056 DOI: 10.1021/jf991222n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Analysis of Raman spectra of oat globulin showed that extreme pH values caused an increase in the amide and C-H stretching band intensity, indicating changes in the secondary structures of the protein due to denaturation. Similar changes were observed when oat globulin was treated with chaotropic salts and several protein perturbants. Sodium dodecyl sulfate, beta-mercaptoethanol, and ethylene glycol also caused a shift in the amide III' band, suggesting a transition from beta-sheet to a random coil conformation. Heating at temperatures near the denaturation temperature of oat globulin led to increases in the amide and C-H band intensity, indicating unfolding of the protein. The data indicate that FT-Raman spectroscopy is suitable for studying the secondary structure of plant proteins such as oat globulin.
Collapse
Affiliation(s)
- C Y Ma
- Food Science Laboratory, Department of Botany, and Department of Chemistry, The University of Hong Kong, Hong Kong.
| | | | | | | |
Collapse
|
42
|
Lyne PD, Karplus M. Determination of the pKa of the 2‘-Hydroxyl Group of a Phosphorylated Ribose: Implications for the Mechanism of Hammerhead Ribozyme Catalysis. J Am Chem Soc 1999. [DOI: 10.1021/ja991820i] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Paul D. Lyne
- Department of Chemistry and Chemical Biology Harvard University, 12 Oxford Street Cambridge, Massachusetts 02138 Physical and Theoretical Chemistry Laboratory Department of Chemistry, Oxford University South Parks Road, Oxford OX1 3QZ, England
| | - Martin Karplus
- Department of Chemistry and Chemical Biology Harvard University, 12 Oxford Street Cambridge, Massachusetts 02138 Physical and Theoretical Chemistry Laboratory Department of Chemistry, Oxford University South Parks Road, Oxford OX1 3QZ, England
| |
Collapse
|
43
|
Renard D, Lefebvre J, Robert P, Llamas G, Dufour E, Dufour E. Structural investigation of beta-lactoglobulin gelation in ethanol/water solutions. Int J Biol Macromol 1999; 26:35-44. [PMID: 10520954 DOI: 10.1016/s0141-8130(99)00060-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The aggregation and gelation properties of beta-lactoglobulin (BLG), a globular protein from milk, was studied in hydro-ethanolic solutions (50/50% (v/v)) at room temperature. The phase state diagrams as a function of pH and ethanol concentration showed that a gel structure appeared after a period ranging from 1 min to 1 week depending on the physico-chemical conditions. The aggregation kinetics, studied by infrared spectroscopy and dynamical rheological measurements, highly depended upon the pH; the process being the fastest at pH 7. Alcohol-induced aggregation of BLG was characterized by the formation of intermolecular hydrogen bonded beta-sheet structures. Small angle neutron scattering indicated that the aggregates structures in the final gels were similar at pH 7, 8 and 9. Through the data obtained at the molecular and macroscopic levels, it can be concluded that the kinetics of gelation were pH dependent while the spatial arrangements of the aggregates were similar in the final structures. The heterogeneous structures formed in hydro-ethanolic gels could be analysed in terms of a phase separation, the syneresis being the final visible state.
Collapse
Affiliation(s)
- D Renard
- Laboratoire de Physico-Chimie des Marcromolécules, Institut National de la Recherche Agronomique, Nantes, France.
| | | | | | | | | | | |
Collapse
|
44
|
Affiliation(s)
- Paul E. Smith
- Department of Biochemistry, Kansas State University, Manhattan, Kansas 66506-3702
| |
Collapse
|
45
|
Sessa DJ, Nelsen TC, Snyder JM. Effect of salts on soy storage proteins defatted with supercritical CO2 and alcohols. J AM OIL CHEM SOC 1998. [DOI: 10.1007/s11746-998-0266-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- David J. Sessa
- ; Plant Polymer Research; NCAUR, USDA, ARS; Peoria Illinois 61604-3902
| | - Terry C. Nelsen
- ; Biometrical Services; NCAUR, USDA, ARS; Peoria Illinois 61604-3902
| | - Janet M. Snyder
- ; Food Quality and Safety Research; NCAUR, USDA, ARS; Peoria Illinois 61604-3902
| |
Collapse
|
46
|
|
47
|
|
48
|
Dufour E, Genot C, Haertlé T. beta-Lactoglobulin binding properties during its folding changes studied by fluorescence spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1205:105-12. [PMID: 8142474 DOI: 10.1016/0167-4838(94)90098-1] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The milk protein, beta-lactoglobulin (BLG) exhibits structural and binding properties which vary widely, depending on the medium. These properties of BLG are reflected in fluorescence intensities, steady-state anisotropies and phase lifetimes of BLG tryptophan residues and of retinol and diphenyl hexatriene (DPH) bound to BLG, as functions of pH, ethanol concentration and protein modifications (22% ethylated, 90% methylated and 85% acetylated BLGs). Tryptophan quenching experiments show that retinol and DPH bind to BLG in 1:1 molar ratios with apparent dissociation constants around 10(-7) - 10(-8) M. The strength of retinol binding is pH-dependent in the range 3-8, whereas that of DPH binding is not. Two different binding sites for these two ligands coexist on the protein. Modified BLGs exhibit higher affinities for DPH than the unmodified protein. At all pH values investigated, the fluorescence emission at 480 nm of retinol/BLG mixtures and retinol, DPH and tryptophan anisotropies and lifetimes change dramatically with midpoint at 27% ethanol for the first parameter and 35% for the others, suggesting simultaneous beta-strand to alpha-helix transition and the dissociation of BLG complexes at 35% ethanol. An intermediate state, possibly 'molten globular', occurs around 20% ethanol, as deduced from anisotropy and lifetime measurements.
Collapse
Affiliation(s)
- E Dufour
- L.E.I.M.A.-Institut National de la Recherche Agronomique, Nantes, France
| | | | | |
Collapse
|
49
|
Dufour E, Robert P, Bertrand D, Haertlé T. Conformation changes of beta-lactoglobulin: an ATR infrared spectroscopic study of the effect of pH and ethanol. JOURNAL OF PROTEIN CHEMISTRY 1994; 13:143-9. [PMID: 8060488 DOI: 10.1007/bf01891973] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Fourier transform infrared spectroscopy has been applied to investigate the secondary structural changes of beta-lactoglobulin in water/ethanol mixtures. The studies were carried out at two different pHs and at high protein concentrations. The spectra were recorded using an attenuated total reflection cell. The amide I band of beta-lactoglobulin in water reveals large amounts of intra extended beta-sheet structure. About 20% ethanol, beta-lactoglobulin unfolds and beta-strand formation is observed. alpha-Helices are built up by increasing the ethanol concentration up to 30%. In 50% ethanol, beta-lactoglobulin gels providing the apparent pH are neutral. The secondary structural changes of beta-lactoglobulin were observed on the similarity maps obtained by Principal Component Analysis.
Collapse
Affiliation(s)
- E Dufour
- LEIMA, Institut National de la Recherche Agronomique, Nantes, France
| | | | | | | |
Collapse
|
50
|
Dufour E, Haertlé T. Temperature-induced folding changes of beta-lactoglobulin in hydro-methanolic solutions. Int J Biol Macromol 1993; 15:293-7. [PMID: 8251444 DOI: 10.1016/0141-8130(93)90029-l] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
It has been demonstrated using circular dichroism that methanol induces important structural changes of beta-lactoglobulin (BLG). The secondary structure of BLG dissolved in 45% methanol (v/v) at 30 degrees C (dielectric constant epsilon approximately 50) is predominantly alpha-helical and unable to complex retinol any more. However, when the dielectric constant of such a medium is raised back to epsilon approximately 70 by decreasing the temperature, both the refolding of BLG into a beta-structure and the formation of the retinol/BLG complex are observed. On the other hand, in the case of BLG solution in 30% methanol, the decrease of the dielectric constant from epsilon approximately 69 to epsilon approximately 53 by heating from 20 degrees C to 60 degrees C leads to the transition from a predominantly beta-structure into a predominantly random one and the dissociation of the retinol/BLG complex. The reversibility of the conformation changes by cooling was demonstrated by circular dichroism curves and tryptophan fluorescence. The retinol fluorescence intensity could not be completely recovered.
Collapse
Affiliation(s)
- E Dufour
- LEIMA, Institut National de la Recherche Agronomique, Nantes, France
| | | |
Collapse
|