scholarly journals Looping-in complexation and ion partitioning in nonstoichiometric polyelectrolyte mixtures

2021 ◽  
Vol 7 (31) ◽  
pp. eabg8654
Author(s):  
Sean Friedowitz ◽  
Junzhe Lou ◽  
Kayla Patricia Barker ◽  
Karis Will ◽  
Yan Xia ◽  
...  
Keyword(s):  
Electrostatic Interactions ◽  
Molecular Model ◽  
Ion Binding ◽  
Ion Partitioning ◽  
Salt Addition ◽  
Low Salt ◽  
The Stability ◽  
Daunting Challenge ◽  
Translational Entropy ◽  
Liquid Liquid Phase Separation

A wide variety of intracellular membraneless compartments are formed via liquid-liquid phase separation of charged proteins and nucleic acids. Understanding the stability of these compartments, while accounting for the compositional heterogeneity intrinsic to cellular environments, poses a daunting challenge. We combined experimental and theoretical efforts to study the effects of nonstoichiometric mixing on coacervation behavior and accurately measured the concentrations of polyelectrolytes and small ions in the coacervate and supernatant phases. For synthetic polyacrylamides and polypeptides/DNA, with unequal mixing stoichiometry, we report a general “looping-in” phenomenon found around physiological salt concentrations, where the polymer concentrations in the coacervate initially increase with salt addition before subsequently decreasing. This looping-in behavior is captured by a molecular model that considers reversible ion binding and electrostatic interactions. Further analysis in the low-salt regime shows that the looping-in phenomenon originates from the translational entropy of counterions that are needed to neutralize nonstoichiometric coacervates.

scholarly journals Contribution of engineered electrostatic interactions to the stability of cytosolic malate dehydrogenase

2001 ◽  
Vol 14 (11) ◽  
pp. 911-917 ◽  
Author(s):  
Francesca Trejo ◽  
Josep Ll. Gelpí ◽  
Albert Ferrer ◽  
Albert Boronat ◽  
Montserrat Busquets ◽  
...  
Keyword(s):  
Malate Dehydrogenase ◽  
Electrostatic Interactions ◽  
The Stability ◽  
Cytosolic Malate Dehydrogenase

scholarly journals The Formation of Chitosan-Coated Rhamnolipid Liposomes Containing Curcumin: Stability and In Vitro Digestion

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 560
Author(s):  
Wei Zhou ◽  
Ce Cheng ◽  
Li Ma ◽  
Liqiang Zou ◽  
Wei Liu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Functional Foods ◽  
Positive Charge ◽  
Physical Stability ◽  
In Vitro Digestion ◽  
Salt Addition ◽  
High Transformation ◽  
Liposomal Delivery ◽  
The Stability

There is growing interest in developing biomaterial-coated liposome delivery systems to improve the stability and bioavailability of curcumin, which is a hydrophobic nutraceutical claimed to have several health benefits. The curcumin-loaded rhamnolipid liposomes (Cur-RL-Lips) were fabricated from rhamnolipid and phospholipids, and then chitosan (CS) covered the surface of Cur-RL-Lips by electrostatic interaction to form CS-coated Cur-RL-Lips. The influence of CS concentration on the physical stability and digestion of the liposomes was investigated. The CS-coated Cur-RL-Lips with RL:CS = 1:1 have a relatively small size (412.9 nm) and positive charge (19.7 mV). The CS-coated Cur-RL-Lips remained stable from pH 2 to 5 at room temperature and can effectively slow the degradation of curcumin at 80 °C; however, they were highly unstable to salt addition. In addition, compared with Cur-RL-Lips, the bioavailability of curcumin in CS-coated Cur-RL-Lips was relatively high due to its high transformation in gastrointestinal tract. These results may facilitate the design of a more efficacious liposomal delivery system that enhances the stability and bioavailability of curcumin in nutraceutical-loaded functional foods and beverages.

Competitive calcium ion binding to end-tethered weak polyelectrolytes

Soft Matter ◽  
2018 ◽  
Vol 14 (12) ◽  
pp. 2365-2378 ◽  
Author(s):  
Rikkert J. Nap ◽  
Sung Hyun Park ◽  
Igal Szleifer
Keyword(s):  
Calcium Ion ◽  
Structural Changes ◽  
Molecular Model ◽  
Ion Concentration ◽  
Ion Binding ◽  
Spherical Nanoparticles ◽  
Planar Surfaces ◽  
Calcium Ion Binding ◽  
Weak Polyelectrolytes

We have developed a molecular model to describe the structural changes and potential collapse of weak polyelectrolyte layers end-tethered to planar surfaces and spherical nanoparticles as a function of pH and divalent ion concentration.

The search for formal electrostatic effects on molecular conformation and crystal packing: crystal structure of 2,2′′-disubstituted (HversusPPh2) 1,1′-(1,2-phenylene)bis(3-methyl-1H-imidazol-3-ium) bis(trifluoromethanesulfonate)

2016 ◽  
Vol 72 (3) ◽  
pp. 198-202
Author(s):  
Carine Duhayon ◽  
Yves Canac ◽  
Laurent Dubrulle ◽  
Carine Maaliki ◽  
Remi Chauvin
Keyword(s):  
Crystal Structure ◽  
Electrostatic Interactions ◽  
Molecular Conformation ◽  
Crystal Packing ◽  
Relative Orientation ◽  
Electron Delocalization ◽  
Electrostatic Effects ◽  
Conformational Freedom ◽  
The Stability ◽  
Bond Character

Electrostatic interactions between localized integral charges make the stability and structure of highly charged small and rigid organics intriguing. Can σ/π-electron delocalization compensate reduced conformational freedom by lowering the repulsion between identical charges? The crystal structure of the title salt, C14H16N42+·2CF3SO3−, (2), is described and compared with that of the 2,2′′-bis(diphenylphosphanyl) derivative, (4). The conformations of the dications and their interactions with neighbouring trifluoromethanesulfonate anions are first analyzed from the standpoint of formal electrostatic effects. Neither cation exhibits any geometrical strain induced by the intrinsic repulsion between the positive charges. In contrast, the relative orientation of the imidazolium rings [i.e. antifor (2) andsynfor (4)] is controlled by different configurations of the interactions with the closest trifluoromethanesulfonate anions. The long-range arrangement is also found to be specific: beyond the formal electrostatic packing, C—H...O and C—H...F contacts have no definite `hydrogen-bond' character but allow the delineation of layers, which are either pleated or flat in the packing of (2) or (4), respectively.

scholarly journals The arrested state of processing bodies supports mRNA regulation in early development

2021 ◽  
Author(s):  
M. Sankaranarayanan ◽  
Ryan J. Emenecker ◽  
Marcus Jahnel ◽  
Irmela R. E. A. Trussina ◽  
Matt Wayland ◽  
...  
Keyword(s):  
Physical Properties ◽  
Electrostatic Interactions ◽  
Processing Bodies ◽  
P Bodies ◽  
Intrinsically Disordered ◽  
Intrinsically Disordered Regions ◽  
Dead Box ◽  
Premature Release ◽  
Liquid Liquid Phase Separation

ABSTRACTBiomolecular condensates that form via liquid-liquid phase separation can exhibit diverse physical states. Despite considerable progress, the relevance of condensate physical states forin vivobiological function remains limited. Here, we investigated the physical properties ofin vivoprocessing bodies (P bodies) and their impact on mRNA storage in matureDrosophilaoocytes. We show that the conserved DEAD-box RNA helicase Me31B forms P body condensates which adopt a less dynamic, arrested physical state. We demonstrate that structurally distinct proteins and hydrophobic and electrostatic interactions, together with RNA and intrinsically disordered regions, regulate the physical properties of P bodies. Finally, using live imaging, we show that the arrested state of P bodies is required to prevent the premature release ofbicoid(bcd) mRNA, a body axis determinant, and that P body dissolution leads tobcdrelease. Together, this work establishes a role for arrested states of biomolecular condensates in regulating cellular function in a developing organism.

scholarly journals Structural basis for osmotic regulation of the DNA binding properties of H-NS proteins

2019 ◽  
Author(s):  
Liang Qin ◽  
Fredj Ben Bdira ◽  
Yann G. J. Sterckx ◽  
Alexander N. Volkov ◽  
Jocelyne Vreede ◽  
...  
Keyword(s):  
Dna Binding ◽  
Electrostatic Interactions ◽  
Intramolecular Interactions ◽  
Structural Basis ◽  
Binding Properties ◽  
Family Protein ◽  
Low Salt ◽  
Functional States ◽  
Mechanistic Basis ◽  
Dna Binding Properties

AbstractH-NS proteins act as osmotic sensors translating changes in osmolarity into altered DNA binding properties, thus, regulating enterobacterial genome organization and genes transcription. The molecular mechanism underlying the switching process and its conservation among H-NS family members remains elusive.Here, we focus on the H-NS family protein MvaT from P. aeruginosa and demonstrate experimentally that its protomer exists in two different conformations, corresponding to two different functional states. In the half-opened state (dominant at low salt) the protein forms filaments along DNA, in the fully opened state (dominant at high salt) the protein bridges DNA. This switching is a direct effect of ionic strengths on electrostatic interactions between the appositively charged DNA binding and N-terminal domains of MvaT. The asymmetric charge distribution and intramolecular interactions are conserved among the H-NS family of proteins. Therefore, our study establishes a general paradigm for the molecular mechanistic basis of the osmosensitivity of H-NS proteins.

scholarly journals Physicochemical Peculiarities of Iodine-Dimethylsulfoxide-H2O Solutions and Effect on Ion Binding to Bovine Serum Albumin

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
K. Grigoryan ◽  
H. Shilajyan
Keyword(s):  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Bovine Serum ◽  
Electrostatic Interactions ◽  
Entropy Change ◽  
Ion Binding ◽  
Fluorescence Energy Transfer ◽  
Iodide Ion ◽  
Different Temperatures ◽  
Fluorescence Energy

The interaction of iodine with bovine serum albumin (BSA) in dimethylsulfoxide (DMSO) aqueous solutions was studied by means of fluorescence and UV/Vis absorption spectroscopy methods. Physicochemical peculiarities of these solutions were revealed. The results showed that the tri-iodide ion formed in the 1DMSO : 2H2O solution caused the fluorescence quenching of BSA. The modified Stern-Volmer quenching constant and corresponding thermodynamic parameters, the free energy change (), enthalpy change (), and entropy change (), at different temperatures (293, 298, and 303 K) were calculated, which indicated that the hydrophobic and electrostatic interactions were the predominant operating forces. The binding locality distance r between BSA and tri-iodide ion at different temperatures was determined based on Förster nonradiation fluorescence energy transfer theory.

scholarly journals Metal Ion-Binding Properties of the Diphosphate Ester Analogue, Methylphosphonylphosphate, in Aqueous Solution

1999 ◽  
Vol 6 (6) ◽  
pp. 321-328 ◽  
Author(s):  
Bin Song ◽  
Jing Zhao ◽  
Fridrich Gregáň ◽  
Nadja Prónayová ◽  
S. Ali A. Sajadi ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Minor Role ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Ph Titration ◽  
Role Based ◽  
The Stability ◽  
A Minor ◽  
Complex Stabilities

The stability constants of the 1:1 complexes formed between methylphosphonylphosphate (MePP3-), CH3P(O)2--O-PO32- , and Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+,​ or Cd2+ (M2+) were determined by potentiometric pH titration in aqueous solution (25 C° ; l = 0.1 M, NaNO3 ). Monoprotonated M(H;MePP) complexes play only a minor role. Based on previously established correlations for M2+ -diphosphate monoester complex-stabilities and diphosphate monoester β-group. basicities, it is shown that the M(Mepp)- complexes for Mg2+ and the ions of the second half of the 3d series, including Zn2+ and Cd2+, are on average by about 0.15 log unit more stable than is expected based on the basicity of the terminal phosphate group in MePP3-. In contrast, Ba(Mepp)- and Sr(Mepp)- are slightly less stable, whereas the stability for Ca(Mepp)- is as expected, based on the mentioned correlation. The indicated increased stabilities are explained by an increased basicity of the phosphonyl group compared to that of a phosphoryl one. For the complexes of the alkaline earth ions, especially for Ba2+, it is suggested that outersphere complexation occurs to some extent. However, overall the M(Mepp)- complexes behave rather as expected for a diphosphate monoester ligand.

scholarly journals Exploiting directional long range secondary forces for regulating electrostatics-dominated noncovalent interactions

2017 ◽  
Vol 8 (2) ◽  
pp. 1378-1390 ◽  
Author(s):  
Mrityunjay K. Tiwari ◽  
Kumar Vanka
Keyword(s):  
Long Range ◽  
Electrostatic Interactions ◽  
Noncovalent Interactions ◽  
Supramolecular Complexes ◽  
The Stability

It has been well established that long range secondary electrostatic interactions (SEIs) have a significant effect on the stability of supramolecular complexes.

Sequence, Salt, Charge, and the Stability of DNA at High Pressure

1996 ◽  
Author(s):  
Robert B. Macgregor Jr ◽  
John Q. Wu
Keyword(s):  
Molar Volume ◽  
Volume Change ◽  
Salt Concentration ◽  
Electrostatic Interactions ◽  
Proposed Model ◽  
Dna Strands ◽  
Positive Volume ◽  
Ion Radius ◽  
The Stability ◽  
Kinetics Of

The effect of pressure on the helix-coil transition temperature (Tm) is reported for the double-stranded polymers poly(dA)poly(dT), poly[d(A-T)], poly[d(l-C], and poly[d(G-C] and triple-stranded poly(dA)2poly(dT). The Tm increases as a function of pressure, implying a positive volume change for the transition and leading to the conclusion that the molar volume of the coil form is larger than the molar volume of the helix. From the change in Tm as a function of pressure, molar volume changes of the transition (ΔVt) are calculated using the Clapeyron equation and calorimetrically determined enthalpies. For the doublestranded polymers, ΔVt, increases in the order poly[d(l-C] < polyt[d(A-T)] < poly(dA)-poly(dT) < polylcl(G-C)]. The value of ΔVt, for the triple-stranded to single-stranded transition of poly(dA) 2poly(dT) is larger than that of poly[d(G-C)I. The magnitude of ΔVt increases with salt concentration in all cases studied; however, the change of ΔVt with salt concentration depends on the sequence of the DNA and the number of strands involved in the transition. In the model proposed to explain the results, the overall molar volume change of the transition is a function of a negative volume change arising from changes in the electrostatic interactions of the DNA strands, and a positive volume change due to unstacking the bases. The model predicted the direction of the change in the ΔVt for several experiments. The magnitude of AVJ increases with counter ion radius, thus for polyld(A-T)], ΔVt, increases in the series Na+ , K+, Cs+, The ΔVt also increases if the charge on the phosphodiester groups is removed. The kinetics of the formation of double-stranded (dA)19(dT)19 in 50 mM NaCI are slowed approximately 14-fold at 200 MPa relative to atmospheric pressure. The implied volume of activation of +37 ml mol−l in the direction of this change is also in agreement with the proposed model. The stability of double- and triple-stranded DNA helices in water around neutral pH depends on the base composition and sequence, as well as on the ionic strength of the solution. Each of these dependencies also defines how DNA interacts with water.

Sign in / Sign up

Export Citation Format

Share Document