Temperature-dependent Self-association Research Articles

Low-Temperature tolerance and conformal adhesion zwitterionic hydrogels as electronic skin for strain and temperature responsiveness

Flexible electronics have been extensively explored for health monitoring, artificial intelligence, and soft robotics. However, it remains challenging to simultaneously achieve temperature and strain monitoring over a wide perception range that are highly analogous to natural human skin. Herein, an intelligent thermosensation zwitterionic hydrogel with superior low-temperature tolerance and conformal adhesion was successfully prepared for strain-temperature dual-modal sensors, based on the temperature-dependent self-association interactions of sulfobetaine methacrylate (SBMA) polymer chains and the incorporation of thermosensitive TEMPO-oxidized cellulose/polyaniline nanofibers (CPA NFs) in glycerol-water binary solvent system. Significantly, the TEMPO-oxidized cellulose acting as the reinforced skeleton guided the in-situ polymerization of polyaniline, while the tunneling current activated by thermal vibration of CPA NFs and the charge transfer caused by the spatial position adjustment collectively contributed to the superimposed signal recognition ability. By leveraging the glycerol molecules to inhibit the ice crystal growth without the compromise of flexibility (1095 %), strain sensitivity (GF = 1.25), and thermal responsiveness (TCR = 2.01% °C−1), the accurate determination paradigm for dual-modal strain and temperature sensor over a wide temperature range (-40–80 °C) was subtlyachieved. Additionally, we corroborated that the conformal adhesion between zwitterionic active sites (e.g. –N+(CH3)3 or -SO3-) and dynamic interfaces was critical for minimizing interface slippage and delamination, as well as maintaining real-time electricalsignal stability. The assembled zwitterionic epidermis sensor array that conformally adhered to fingers could realize the subtle signal identification and localized temperature detection, which presented promising prospects for designing the multi-modal skin-like responsiveness electronic skins that suitable for harsh temperature conditions.

The Inherent Dynamics and Interaction Sites of the SARS-CoV-2 Nucleocapsid N-Terminal Region

The nucleocapsid protein is one of four structural proteins encoded by SARS-CoV-2 and plays a central role in packaging viral RNA and manipulating the host cell machinery, yet its dynamic behavior and promiscuity in nucleotide binding has made standard structural methods to address its atomic-resolution details difficult. To begin addressing the SARS-CoV-2 nucleocapsid protein interactions with both RNA and the host cell along with its dynamic behavior, we have specifically focused on the folded N-terminal domain (NTD) and its flanking regions using nuclear magnetic resonance solution studies. Studies performed here reveal a large repertoire of interactions, which includes a temperature-dependent self-association mediated by the disordered flanking regions that also serve as binding sites for host cell cyclophilin-A while nucleotide binding is largely mediated by the central NTD core. NMR studies that include relaxation experiments have revealed the complicated dynamic nature of this viral protein. Specifically, while much of the N-terminal core domain exhibits micro-millisecond motions, a central β-hairpin shows elevated inherent flexibility on the pico-nanosecond timescale and the serine/arginine-rich region of residues 176–209 undergoes multiple exchange phenomena. Collectively, these studies have begun to reveal the complexities of the nucleocapsid protein dynamics and its preferred interaction sites with its biological targets.

Cold and distant: structural features of the nucleoprotein complex of a cold-adapted influenza A virus strain

Two influenza A nucleoprotein variants (wild-type: G102R; and mutant: G102R and E292G) were studied with regard to macro-molecular interactions in oligomeric form (24-mers). The E292G mutation has been previously shown to provide cold adaptation. Molecular dynamics simulations of these complexes and trajectory analysis showed that the most significant difference between the obtained models was distance between nucleoprotein complex strands. The isolated complexes of two ribonucleoprotein variants were characterized by transmission electron microscopy and differential scanning fluorimetry (DSF). Presence of the E292G substitution was shown by DSF to affect nucleoprotein complex melting temperature. In the filament interface peptide model, it was shown that the peptide corresponding in primary structure to the wild-type NP (SGYDF E REGYS) is prone to temperature-dependent self-association, unlike the peptide corresponding to E292G substitution (SGYDF G REGYS). It was also shown that the SGYDF E REGYS peptide is capable of interacting with a monomeric nucleoprotein (wild type); this interaction’s equilibrium dissociation constant is five orders of magnitude lower than for the SGYDF G REGYS peptide. Using small-angle neutron scattering (SANS), the supramolecular structures of isolated complexes of these proteins were studied at temperatures of 15, 32, and 37 °C. SANS data show that the structures of the studied complexes at elevated temperature differ from the rod-like particle model and react differently to temperature changes. The data suggest that the mechanism behind cold adaptation with E292G is associated with a weakening of the interaction between strands of the ribonucleoprotein complex and, as a result, the appearance of inter-chain interface flexibility necessary for complex function at low temperature. Communicated by Ramaswamy H. Sarma

Impact of Blend Proportion on the Miscibility and Thermal Characteristics of Synthetic Plastic-Derived Polypentapeptide with Commercially Available Polyvinyl Alcohol

Plastic-based polypeptides are versatile entities formed to conceive a broad range of scaffold biomaterials. They possess distinct, repetitive, hydrophobic sequences that confer conservation, reversibility, temperature-dependent self-association and dissociation properties. The repeating sequence of plastic-based peptides, poly(AVGVP) have been synthesized by the solution phase method and characterized by 13C and 1H-NMR spectroscopy. The intermolecular interactions between poly(AVGVP) and polyvinyl alcohol (PVA) was explored in solution and solid phase by diverse analytical methods. The interaction parameters, namely; α, β, µ and ∆[η]m obtained from the dilute solution viscometric approach, unveiled that the two polymers were miscible up to 40% of the polypeptide in the blends. Besides, Fourier transform infrared (FTIR) spectroscopy authenticated the formation of strong intermolecular hydrogen bonds connecting blend networks. Further, other analytical techniques such as DSC, SEM and XRD probes advocated the miscibility results. Thermogravimetric investigation of the blends confirmed the proportionate decrease of the thermal stability with the increase of polypentapeptide, attributable to the intermolecular amalgamation between the polypeptide and PVA. The blends and plain poly(AVGVP) degraded completely at about 700 °C, whereas the virgin PVA was about only 60% at this temperature.

Stepwise Mechanism of Temperature-Dependent Coacervation of the Elastin-like Peptide Analogue Dimer, (C(WPGVG)3)2.

Elastin-like peptides (ELPs) are distinct, repetitive, hydrophobic sequences, such as (VPGVG) n, that exhibit coacervation, the property of reversible, temperature-dependent self-association and dissociation. ELPs can be found in elastin and have been developed as new scaffold biomaterials. However, the detailed relationship between their amino acid sequences and coacervation properties remains obscure because of the structural flexibility of ELPs. In this study, we synthesized a novel, dimeric ELP analogue (H-C(WPGVG)3-NH2)2, henceforth abbreviated (CW3)2, and analyzed its self-assembly properties and structural factors as indicators of coacervation. Turbidity measurements showed that (CW3)2 demonstrated coacervation at a concentration much lower than that of its monomeric form and another ELP. In addition, the coacervate held water-soluble dye molecules. Thus, potent and distinct coacervation was obtained with a remarkably short sequence of (CW3)2. Furthermore, fluorescence microscopy, dynamic light scattering, and optical microscopy revealed that the coacervation of (CW3)2 was a stepwise process. The structural factors of (CW3)2 were analyzed by molecular dynamics simulations and circular dichroism spectroscopy. These measurements indicated that helical structures primarily consisting of proline and glycine became more disordered at high temperatures with concurrent, significant exposure of their hydrophobic surfaces. This extreme change in the hydrophobic surface contributes to the potent coacervation observed for (CW3)2. These results provide important insights into more efficient applications of ELPs and their analogues, as well as the coacervation mechanisms of ELP and elastin.

Interactions of Dodecylphosphocholine with Lipid Membranes

As a bio-analogous surfactant, n-dodecylphopsphocholine (abbreviated DPC, LPC, or FOS-choline-12) has been proven useful for membrane protein studies. We present a detailed characterization of its temperature-dependent self-association (CMC, deltaCp) and its interaction with liposomes. We describe membrane partitioning, membrane permeation, membrane permeabilization (i.e., leakage to aqueous solutes), membrane lysis/solubilization to micelles and structural aspects by means of ITC (demicellization, uptake-and-release, solubilization-and-reconstitution assays), static and dynamic light scattering (NIBS), the lifetime-based dye leakage assay (for details on the method see Soft Matter 2009, 5:2849), and the time-resolved fluorescence anisotropy of membrane probes. The results are important for the optimization of membrane protein solubilization and reconstitution into proteoliposomes.

Small-Angle X-ray Scattering and Rheological Characterization of Aqueous Lignosulfonate Solutions

Lignosulfonate is a colloidal polyelectrolyte widely used as a dispersant in various industrial applications and produced during chemical pulping of wood chips. Here we present a systematic small-angle X-ray scattering (SAXS) and rheological study of fractionated lignosulfonate (mass weighted molar mass M w 18 000 g/mol) dissolved in water and 0.2 M NaCl. The concentration range varied from semidilute to concentrated regime. SAXS intensity of all solutions followed the Porod law at all concentrations, which is a clear indication of a compact shape of the lignosulfonate particle. In water, below 10 mass % lignosulfonate, the average interparticle distance obtained from SAXS patterns relates to concentration via a power law with exponent -0.28. Deviation of the power law exponent from ideal -0.33 and a linear decrease in volume fraction normalized Porod constant as a function of concentration are taken as indications of self-association of lignosulfonate. In saline solutions at high lignosulfonate mass fractions the average distance between lignosulfonate particles was longer and the average particle size was larger than those in aqueous solutions. The intrinsic viscosity in saline solution also was larger than that in aqueous solution. Lignosulfonate solutions showed Newtonian viscosity, except at very high concentrations. The variation of the relative zero-shear viscosity eta(0),r) with concentration was interpreted with the Krieger-Dougherty equation. An oblate spheroid shape with an axial ratio of 3.5 describes the average shape of the lignosulfonate particles in saline solutions based on SAXS intensities, the size distribution obtained using gel permeation chromatography, and rheological characterization. The largest dimension of the particles was about 8 nm. SAXS and rheology studies as a function of temperature reveal indications of temperature-dependent self-association.

Thermal dependency of RAG1 self-association properties

BackgroundFunctional immunoglobulin and T cell receptor genes are produced in developing lymphocytes by V(D)J recombination. The initial site-specific DNA cleavage steps in this process are catalyzed by the V(D)J recombinase, consisting of RAG1 and RAG2, which is directed to appropriate DNA cleavage sites by recognition of the conserved recombination signal sequence (RSS). RAG1 contains both the active site and the RSS binding domains, although RAG2 is also required for DNA cleavage activity. An understanding of the physicochemical properties of the RAG proteins, their association, and their interaction with the RSS is not yet well developed.ResultsHere, we further our investigations into the self-association properties of RAG1 by demonstrating that despite the presence of multiple RAG1 oligomers, only the dimeric form maintains the ability to interact with RAG2 and the RSS. However, facile aggregation of the dimeric form at physiological temperature may render this protein inactive in the absence of RAG2. Upon addition of RAG2 at 37°C, the preferentially stabilized V(D)J recombinase:RSS complex contains a single dimer of RAG1.ConclusionTogether these results confirm that the functional form of RAG1 in V(D)J recombination is in the dimeric state, and that its stability under physiological conditions likely requires complex formation with RAG2. Additionally, in future structural and functional studies of RAG1, it will be important to take into account the temperature-dependent self-association properties of RAG1 described in this study.

Self-association and Chaperone Activity of Hsp27 Are Thermally Activated

The small heat shock protein 27 (Hsp27) is an oligomeric, molecular chaperone in vitro. This chaperone activity and other physiological roles attributed to Hsp27 have been reported to depend on the state of self-association. In the present work, we have used sedimentation velocity experiments to demonstrate that the self-association of Hsp27 is independent of pH and ionic strength but increases significantly as the temperature is increased from 10 to 40 degrees C. The largest oligomers formed at 10 degrees C are approximately 8-12 mer, whereas at 40 degrees C oligomers as large as 22-30 mer are observed. Similarly, the chaperone activity of Hsp27 as indicated by its ability to inhibit dithiothreitol-induced insulin aggregation also increases with increased temperature, with a particularly sharp increase in activity as temperature is increased from 34 to 43 degrees C. Similar studies of an Hsp27 triple variant that mimics the behavior of the phosphorylated protein establish that this protein has greatly diminished chaperone activity that responds minimally to increased temperature. We conclude that Hsp27 can exploit a large number of oligomerization states and that the range of oligomer size and the magnitude of chaperone activity increase significantly as temperature is increased over the range that is relevant to the physiological heat shock response.

The Effect of C-Terminal Deletion on the Folding and Self-association of Recombinant Non-phosphorylated Human ß-Casein

Recombinant human beta-casein (CN) mutants were prepared having 11, 22 and 31 amino acids (aa) deleted from the C-terminus. The temperature-dependent self-association of these and the wild-type recombinant was studied by turbidity (OD400) while possible folding differences were examined by intrinsic and extrinsic fluorescence intensity and fluorescence resonance energy transfer. There were major self-association and some conformational differences. Hydrophobicity profile and hydrophobic cluster analysis for bovine and human beta-CN suggested that the ability of the 31 aa deletion mutant in human beta-CN to self-associate when a comparable bovine deletion peptide would not may be due to the presence of additional hydrophobic regions in the middle, indicating that the human protein may contain more than a single hydrophobic binding locus and suggesting that the process for the formation and structure of the micelles of human milk may be quite different from that for bovine milk. A new model may be needed.

Effects of non-covalent self-association on the subcutaneous absorption of a therapeutic peptide.

To utilize an acylated peptide as a model system to investigate the relationships among solution peptide conformation, non-covalent self-association, subcutaneous absorption and bioavailability under pharmaceutically relevant solution formulation conditions. CD spectroscopy, FTIR spectroscopy, equilibrium sedimentation, dynamic light scattering, and size exclusion chromatography were employed to characterize the effects of octanoylation on conformation and self-association of the 31 amino acid peptide derivative des-amino-histidine(7) arginine(26) human glucagon-like peptide (7-37)-OH (IP(7)R(26)GLP-1). Hyperglycemic clamp studies were performed to compare the bioavailability, pharmacokinetics, and pharmacodynamics of solution formulations of oct-IP(7)R(26)GLP-1 administered subcutaneously to normal dogs. Octanoylation of IP(7)R(26)GLP-1 was shown to confer the propensity for a major solvent-induced conformational transition with an accompanying solvent- and temperature-dependent self-association behavior. Formulations were characterized that give rise to remarkably different pharmacodynamics and pharmacokinetics that correlate with distinct peptide conformational and self-association states. These states correspond to: (i) a minimally associated alpha-helical form (apparent molecular weight = 14 kDa), (ii) a highly associated, predominantly beta-sheet form (effective molecular diameter 20 nm), and (iii) an unusually large, micelle-like soluble beta-sheet aggregate (effective molecular diameter 50 nm). Bioavailability and pharmacokinetics of a self-associating peptide can be influenced by aggregate size and the ease of disruption of the non-covalent intermolecular interactions at the subcutaneous site. Hydrophobic aggregation mediated by seemingly innocuous solution formulation conditions can have a dramatic effect on the subcutaneous bioavailability and pharmacokinetics of a therapeutic peptide and in the extreme, can totally preclude its absorption. A size exclusion chromatographic method is identified that distinguishes subcutaneously bioavailable aggregated oct-IP(7)R(26)GLP-1 from non-bioavailable aggregated oct-IP(7)R(26)GLP-1.

ChemInform Abstract: TEMPERATURE‐DEPENDENT SELF‐ASSOCIATION OF DODECYLAMMONIUM PROPIONATE IN BENZENE AND CYCLOHEXANE

Chemischer InformationsdienstVolume 7, Issue 5 Article ChemInform Abstract: TEMPERATURE-DEPENDENT SELF-ASSOCIATION OF DODECYLAMMONIUM PROPIONATE IN BENZENE AND CYCLOHEXANE FRED YUN-FAT LO, FRED YUN-FAT LOSearch for more papers by this authorBARNEE M. ESCOTT, BARNEE M. ESCOTTSearch for more papers by this authorELEANOR J. FENDLER, ELEANOR J. FENDLERSearch for more papers by this authorE. T. JUN. ADAMS, E. T. JUN. ADAMSSearch for more papers by this authorRUSSELL D. LARSEN, RUSSELL D. LARSENSearch for more papers by this authorPHILIP W. SMITH, PHILIP W. SMITHSearch for more papers by this author FRED YUN-FAT LO, FRED YUN-FAT LOSearch for more papers by this authorBARNEE M. ESCOTT, BARNEE M. ESCOTTSearch for more papers by this authorELEANOR J. FENDLER, ELEANOR J. FENDLERSearch for more papers by this authorE. T. JUN. ADAMS, E. T. JUN. ADAMSSearch for more papers by this authorRUSSELL D. LARSEN, RUSSELL D. LARSENSearch for more papers by this authorPHILIP W. SMITH, PHILIP W. SMITHSearch for more papers by this author First published: February 3, 1976 https://doi.org/10.1002/chin.197605067AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume7, Issue5February 3, 1976 RelatedInformation

Temperature-dependent self-association of dodecylammonium propionate in benzene and cyclohexane

Temperature-dependent self-association of dodecylammonium propionate in benzene and cyclohexane

The temperature-dependent self-association of β-lactoglobulin C in glycine buffers

The self-association of β-lactoglobulin C at low pH (ca. 2.5) in glycine buffers has been studied at four temperatures, 10, 16, 20, and 25 °C, by low- and high-speed sedimentation equilibrium experiments. One buffer had an ionic strength of 0.1 and the other an ionic strength of 0.2. With either buffer the concentration dependence of the apparent weight average molecular weight, M wa, was characteristic of a nonideal self-association. Like its genetic variants, β-lactoglobulin A and B, the self-association of β-lactoglobulin C increased with decreasing temperature; however, at the same temperature the association was always stronger in the buffer having the higher ionic strength. Several models were used to test the self-association, and a monomer-dimer self-association seemed to describe the self-association best with either buffer. Values of the association equilibrium constant, K 2, and the second virial coefficient, BM 1, are reported at each temperature for both series of experiments. Values of the thermodynamic functions, ΔG °, ΔH °, and ΔS °, are also reported for these experiments.

The temperature-dependent self-association of adenosine 5'triphosphate in 0.154 M NaCl

The disodium salt of adenosine 5'triphosphate (ATP), dissolved in and dialyzed against isotonic saline, undergoes a temperature-dependent self-association. Self-association increases with decreasing temperature. The technical achievement that made these experiments possible was the development and availability of a hollow fiber dialyzer with a low molecular weight (200) cutoff. Several models were tested to describe the experimental data, and a monomer-dirner-trimer association seemed to describe the data best- Both the dimerization and trimerization were exothermic; values of the thermodynamic functions for these reactions are reported. The self-association reaction for ATP is much stronger than that observed for purine and cyridine, as well as for various nucleosides whose self-association in aqueous solutions has been studied.

Sedimentation equilibrium in reacting systems. VII. The temperature-dependent self-association of β-lactoglobulin A at pH 2.46

The self-association of β-lactoglobulin A in 0.2 m glycine buffer (pH 2.46 at 23.5 °C) has been studied by low speed sedimentation equilibrium experiments at 11, 16, 20, 25 °C. In all four sets of experiments the concentration dependence of the apparent weight average molecular weight, M wa, was indicative of a nonideal self-association. The association decreased with increasing temperature. Several models to describe the observed self-association were tested, and a monomer-dimer association describes the data best. Values of the association equilibrium constant, K 2, and the second virial coefficient, BM 1, are reported at each temperature. Values of the thermodynamic functions, ΔG °, ΔH °, and ΔS °, are also reported for these experiments.