Conformational changes in humic acids in aqueous solutions

AbstractConformational changes in humic acids in two different aqueous solutions (NaCl and NaOH) are studied by means of high resolution ultrasound spectrometry. The method is based on the measurement of parameters of ultrasonic waves propagating through the sample. The attenuation describes the decay of the amplitude of the ultrasonic wave with the distance travelled. The velocity is the speed of this wave and is related to the wavelength and the frequency of oscillation of the deformation. It is determined by the density and elasticity of the sample, which is strongly influenced by the molecular arrangement. The minimal velocity of ultrasound was observed at 1 g dm−3 for lignitic humic acids and at 0.5 g dm−3 for IHSS Leonardite standard. The values of compressibility as computed are almost constant up to humic acids’ content corresponding to the minimum velocity of ultrasound and then decrease with the increase in concentration. This shows that the organisation of particles in diluted and concentrated humic acids sols is different. The decrease in compressibility points to the formation of a more rigid structure, which could lead to the decrease in humic acids’ binding ability. It was confirmed that the method employed was very sensitive and could be utilised as an indicator of conformational changes in humic acids in solutions with varying concentrations.

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High resolution nuclear magnetic resonance studies of platinum(II) – guanosine-5′-monophosphate interactions in aqueous solutions

Canadian Journal of Chemistry ◽

10.1139/v81-486 ◽

1981 ◽

Vol 59 (23) ◽

pp. 3297-3302 ◽

Cited By ~ 13

Author(s):

Moschos Polissiou ◽

Minh Tan Phan Viet ◽

Maurice St-Jacques ◽

Theophile Theophanides

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

High Resolution ◽

Aqueous Solutions ◽

Conformational Changes ◽

Coupling Constant ◽

Magnetic Resonance Studies ◽

H Nmr ◽

Nmr Study ◽

Ribose Moiety

A detailed 400 MHz 1H nmr study was carried out on platinum complexation products of GMP by K2PtCl4. Coupling constant values show that platination on N7 induces a conformational change on the ribose moiety: the 3E form of the ring and the gt conformer about the C(4′)—C(5′) bond are favoured upon complexation. The results are compared to the conformational changes induced by N7 protonation and methylation.

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Complexation of Copper(II) with Humic Acids Studied by Ultrasound Spectrometry

Organic Chemistry International ◽

10.1155/2012/206025 ◽

2012 ◽

Vol 2012 ◽

pp. 1-6 ◽

Cited By ~ 5

Author(s):

Martina Klučáková

Keyword(s):

Humic Acid ◽

Humic Acids ◽

Conformational Changes ◽

Ph Value ◽

Biologically Active ◽

Copper Binding ◽

Binding Ability ◽

Initial Ph ◽

The Individual ◽

Concentrated Systems

Copper biogeochemistry is controlled by bonding to natural organic matter. The soluble forms of bonded copper can be more biologically active due to the higher migration in environmental systems and instability of some copper-humic complexes. In this work, the interactions of copper(II) ions with humic acids are studied by means of high-resolution ultrasound spectrometry. It was found that the stoichiometry of the formed complexes is strongly influenced by the organization of humic acid in solution and by the final pH value in equilibrium. Although the ratio between the added copper and humic acids in all used concentrations was constant and the initial pH value was neutral, we observed significant differences between the individual systems. The highest binding ability was determined for a humic content of 0.5 g·dm−3. More diluted and more concentrated systems were able to bind lower amounts of copper. The implemented method is very sensitive and can be utilized not only for monitoring copper binding but also as an indicator of conformational changes of humic acid in solutions with varying concentration.

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Study of polymer chain dynamics in solution by time-resolved spectrofluorometry

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19893011 ◽

1989 ◽

Vol 54 (11) ◽

pp. 3011-3024 ◽

Cited By ~ 1

Author(s):

Vlastimil Fidler ◽

Stefan Vajda ◽

Zuzana Limpouchová ◽

Jiří Dvořák ◽

Karel Procházka ◽

...

Keyword(s):

Aqueous Solutions ◽

Conformational Changes ◽

Methacrylic Acid ◽

Correlation Time ◽

General Level ◽

Polymeric Chain ◽

Relative Molecular Mass ◽

Chain Dynamics ◽

Time Resolved ◽

Covalently Bonded

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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Studies of Conformational Changes of Tubulin Induced by Interaction with Kinesin Using Atomistic Molecular Dynamics Simulations

International Journal of Molecular Sciences ◽

10.3390/ijms22136709 ◽

2021 ◽

Vol 22 (13) ◽

pp. 6709

Author(s):

Xiao-Xuan Shi ◽

Peng-Ye Wang ◽

Hong Chen ◽

Ping Xie

Keyword(s):

Molecular Dynamics ◽

High Resolution ◽

Binding Energy ◽

Molecular Dynamics Simulations ◽

Conformational Changes ◽

Weak Interactions ◽

Molecular Motor ◽

Structural Data ◽

Calculated Binding Energy ◽

Dynamics Simulations

The transition between strong and weak interactions of the kinesin head with the microtubule, which is regulated by the change of the nucleotide state of the head, is indispensable for the processive motion of the kinesin molecular motor on the microtubule. Here, using all-atom molecular dynamics simulations, the interactions between the kinesin head and tubulin are studied on the basis of the available high-resolution structural data. We found that the strong interaction can induce rapid large conformational changes of the tubulin, whereas the weak interaction cannot. Furthermore, we found that the large conformational changes of the tubulin have a significant effect on the interaction of the tubulin with the head in the weak-microtubule-binding ADP state. The calculated binding energy of the ADP-bound head to the tubulin with the large conformational changes is only about half that of the tubulin without the conformational changes.

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