Nano- and microcomplexes of biopolymer carrageenans and dodecylammonium chloride

2011 ◽  
Vol 31 (2-3) ◽  
Author(s):  
Marko Vinceković ◽  
Marija Bujan ◽  
Maja Dutour Sikirić
Keyword(s):  
Hydrophobic Interactions ◽  
Intermolecular Forces ◽  
Model Systems ◽  
Molar Ratio ◽  
Giant Vesicles ◽  
Linear Charge Density ◽  
Ordered Structures ◽  
Electrostatic And Hydrophobic Interactions ◽  
New Compounds ◽  
Gel Network

Abstract Polymer and surfactant complexation was investigated in systems containing anionic biopolymers and cationic surfactants by various classical and modern methods. Differently charged carrageenans (one, two or three sulfate groups per monomeric unit) and dodecylammonium chloride (DDACl) were used as model systems. Formation of various soluble and insoluble complexes (from nano- to microdimensions) and gelation strongly depends on carrageenan and DDACl concentrations, their molar ratio and linear charge density on carrageenan chains. The main factors governing complexation include electrostatic and hydrophobic interactions as well as conformation of carrageenan chains. With increasing carrageenan concentration, the intramacromolecular complexes change to intermacromolecular, which subsequently reorganize into better ordered structures, giant vesicles, and precipitated stoichiometric compounds, dodecylammonium carrageenates. Structural analysis of the new compounds revealed the formation of a lamellar structure with the polar sublayer containing carrageenan chains and the non-polar sublayer consisting of disordered dodecylammonium chains electrostatically attached to the carrageenan backbone. At gelling carrageenan concentration, progressive addition of DDACl caused gradual transitions from the structure of carrageenan gel alone to lamellar ordering of collapsed gel balanced by intermolecular forces within the gel network, i.e., by hydrogen bonding, electrostatic, hydrophobic and van der Waals forces.

Interaction of sulphone based reactive dyes with cationic surfactant: a spectroscopic and conductometric study

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Misbah Iram ◽  
Hamadia Sultana ◽  
Muhammad Usman ◽  
Bazgha Ahmad ◽  
Nadia Akram ◽  
...  
Keyword(s):  
Strong Interaction ◽  
Cetyltrimethylammonium Bromide ◽  
Hydrophobic Interactions ◽  
Reactive Dyes ◽  
Micellar System ◽  
Palisade Layer ◽  
Micellar Systems ◽  
Gibbs Energies ◽  
Electrostatic And Hydrophobic Interactions ◽  
Conductometric Study

Abstract Interaction of sulphone based reactive dyes, designated as dye-1 and dye-2, with cationic micellar system of cetyltrimethylammonium bromide (CTAB), has been investigated by spectroscopic and conductometeric measurements. Efficiency of the selected micellar systems is assessed by the values of binding constant (K b ), partition coefficient (K x ) and respective Gibbs energies. Critical micelle concentration (CMC) of surfactant, electrostatic and hydrophobic interactions as well as polarity of the medium plays significant role in this phenomenon. The negative values of Gibbs energies of binding (∆G b ) and partition (∆G p ) predicts the feasibility and spontaneity of respective processes. Similarly negative values of ∆G m and ∆H m and positive values of ∆S m , calculated from conductometeric data, further, revealed the exothermicity, spontaneity and, thus, stability of system. The results, herein, have disclosed the strong interaction between dye and surfactant molecules. The dye-2 has been observed to be solubilized to greater extent, as compared to dye 1, due to strong interaction ith hydrophiles of CTAB and accommodation of its molecules in palisade layer of micelle closer to the micelle/water interface.

scholarly journals Reaktive E=C(p–p)π Systeme, XXXIV Addition von Alkoholen oder primären Aminen an Phosphaalkene F3CP=C(F)OR. Neue Trifluormethylphosphane und -phosphaalkene/Reactive E = C( p – p ) π-Systems, XXXIV Addition of Alcohols or Primary Amines to Phosphaalkenes F3CP= C(F)OR . Novel Trifluoromethylphosphanes and Phosphaalkenes

1993 ◽  
Vol 48 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Joseph Grobe ◽  
Duc Le Van ◽  
Gudrun Lange
Keyword(s):  
High Resolution Mass Spectrometry ◽  
Molar Ratio ◽  
Primary Amines ◽  
The Novel ◽  
Experimental Conditions ◽  
Pull System ◽  
Fragment Ions ◽  
New Compounds ◽  
C Nmr

The course of the reactions o f fluorophosphaalkenes F3CP = C (F)OR [R = Me (1), Et (2)] with methanol or ethanol strongly depends on the experimental conditions. Thus at 70 °C a mixture of the 2-phosphapropionic acid ester F3CP (H )CO2R [R = Me (3), Et (4)] and trifluoromethylphosphane H2PCF3 is formed [molar ratio: 3 or 4 /H2 CF3 ≈1/1]. If the precursors F3CP (H )CO2R [R = Me (3), Et) are used as starting materials, the reaction with ROH under the same conditions affords 3 and 4, respectively, (90 to 95% yield) with only traces of H2PCF 3. In the presence o f iPr2NH these precursors react with R′OH to give the novel trifluoromethylphosphaalkenes F3CP = C (OR )OR [R /R′: Me/Me (6); E t/E t (7); Me/Et (8)]. With Et2NH , 3 undergoes an addition/elimination process yielding the interesting push/pull system Et2N(F)C = P-CO2Me (5). 1 and 2 react with primary amines R′NH2 (R′= tBu, Me) with stereoselective formation of the fairly labile phosphaalkenes F3CP = C(OR)NHR′ [R /R′: Me/tBu (9), Et/tBu(10), Me/Me (11)] with trans-positions for CF3 and NHR′.The new compounds 3 -11 were characterized by spectroscopic investigations (1H , 19F, 31P, 13C NMR ; IR, MS) and determination of M+ or typical fragment ions [M+ -OR ] by high resolution mass spectrometry.

Intermolecular forces in biology

2001 ◽  
Vol 34 (2) ◽  
pp. 105-267 ◽  
Author(s):  
Deborah Leckband ◽  
Jacob Israelachvili
Keyword(s):  
Hydrophobic Interactions ◽  
Intermolecular Forces ◽  
Biological Molecules ◽  
Biological Macromolecules ◽  
Chemical Transformations ◽  
Adhesion Forces ◽  
Multiple Bonds ◽  
Membrane Surfaces ◽  
In Series ◽  
Non Equilibrium

0. Abbreviations 1061. Introduction: overview of forces in biology 1081.1 Subtleties of biological forces and interactions 1081.2 Specific and non-specific forces and interactions 1131.3 van der Waals (VDW) forces 1141.4 Electrostatic and ’double-layer‘ forces (DLVO theory) 1221.4.1 Electrostatic and double-layer interactions at very small separation 1261.5 Hydration and hydrophobic forces (structural forces in water) 1311.6 Steric, bridging and depletion forces (polymer-mediated and tethering forces) 1371.7 Thermal fluctuation forces: entropic protrusion and undulation forces 1421.8 Comparison of the magnitudes of the major non-specific forces 1461.9 Bio-recognition 1461.10 Equilibrium and non-equilibrium forces and interactions 1501.10.1 Multiple bonds in parallel 1531.10.2 Multiple bonds in series 1552. Experimental techniques for measuring forces between biological molecules and surfaces 1562.1 Different force-measuring techniques 1562.2 Measuring forces between surfaces 1612.3 Measuring force–distance functions, F(D) 1612.4 Relating the forces between different geometries: the ‘Derjaguin Approximation’ 1622.5 Adhesion forces and energies 1642.5.1 An example of the application of adhesion mechanics of biological adhesion 1662.6 Measuring forces between macroscopic surfaces: the surface forces apparatus (SFA) 1672.7 The atomic force microscope (AFM) and microfiber cantilever (MC) techniques 1732.8 Micropipette aspiration (MPA) and the bioforce probe (BFP) 1772.9 Osmotic stress (OS) and osmotic pressure (OP) techniques 1792.10 Optical trapping and the optical tweezers (OT) 1812.11 Other optical microscopy techniques: TIRM and RICM 1842.12 Shear flow detachment (SFD) measurements 1872.13 Cell locomotion on elastically deformable substrates 1893. Measurements of equilibrium (time-independent) interactions 1913.1 Long-range VDW and electrostatic forces (the two DVLO forces) between biosurfaces 1913.2 Repulsive short-range steric–hydration forces 1973.3 Adhesion forces due to VDW forces and electrostatic complementarity 2003.4 Attractive forces between surfaces due to hydrophobic interactions: membrane adhesion and fusion 2093.4.1 Hydrophobic interactions at the nano- and sub-molecular levels 2113.4.2 Hydrophobic interactions and membrane fusion 2123.5 Attractive depletion forces 2133.6 Solvation (hydration) forces in water: forces associated with water structure 2153.7 Forces between ‘soft-supported’ membranes and proteins 2183.8 Equilibrium energies between biological surfaces 2194. Non-equilibrium and time-dependent interactions: sequential events that evolve in space and time 2214.1 Equilibrium and non-equilibrium time-dependent interactions 2214.2 Adhesion energy hysteresis 2234.3 Dynamic forces between biomolecules and biomolecular aggregates 2264.3.1 Strengths of isolated, noncovalent bonds 2274.3.2 The strengths of isolated bonds depend on the activation energy for unbinding 2294.4 Simulations of forced chemical transformations 2324.5 Forced extensions of biological macromolecules 2354.6 Force-induced versus thermally induced chemical transformations 2394.7 The rupture of bonds in series and in parallel 2424.7.1 Bonds in series 2424.7.2 Bonds in parallel 2444.8 Dynamic interactions between membrane surfaces 2464.8.1 Lateral mobility on membrane surfaces 2464.8.2 Intersurface forces depend on the rate of approach and separation 2494.9 Concluding remarks 2535. Acknowledgements 2556. References 255While the intermolecular forces between biological molecules are no different from those that arise between any other types of molecules, a ‘biological interaction’ is usually very different from a simple chemical reaction or physical change of a system. This is due in part to the higher complexity of biological macromolecules and systems that typically exhibit a hierarchy of self-assembling structures ranging in size from proteins to membranes and cells, to tissues and organs, and finally to whole organisms. Moreover, interactions do not occur in a linear, stepwise fashion, but involve competing interactions, branching pathways, feedback loops, and regulatory mechanisms.

Structure, stability and folding of the α-helix

2001 ◽  
Vol 68 ◽  
pp. 95-110 ◽  
Author(s):  
Andrew J. Doig ◽  
Charles D. Andrew ◽  
Duncan A. E. Cochran ◽  
Eleri Hughes ◽  
Simon Penel ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Hydrophobic Interactions ◽  
Data Bank ◽  
Site Directed Mutagenesis ◽  
Model Systems ◽  
Side Chain ◽  
Structure Stability ◽  
Helical Peptides ◽  
Vast Number ◽  
Α Helix

Pauling first described the α-helix nearly 50 years ago, yet new features of its structure continue to be discovered, using peptide model systems, site-directed mutagenesis, advances in theory, the expansion of the Protein Data Bank and new experimental techniques. Helical peptides in solution form a vast number of structures, including fully helical, fully coiled and partly helical. To interpret peptide results quantitatively it is essential to use a helix/coil model that includes the stabilities of all these conformations. Our models now include terms for helix interiors, capping, side-chain interactions, N-termini and 310-helices. The first three amino acids in a helix (N1, N2 and N3) and the preceding N-cap are unique, as their amide NH groups do not participate in backbone hydrogen bonding. We surveyed their structures in proteins and measured their amino acid preferences. The results are predominantly rationalized by hydrogen bonding to the free NH groups. Stabilizing side-chain-side-chain energies, including hydrophobic interactions, hydrogen bonding and polar/non-polar interactions, were measured accurately in helical peptides. Helices in proteins show a preference for having approximately an integral number of turns so that their N- and C-caps lie on the same side. There are also strong periodic trends in the likelihood of terminating a helix with a Schellman or αL C-cap motif. The kinetics of α-helix folding have been studied with stopped-flow deep ultraviolet circular dichroism using synchrotron radiation as the light source; this gives a far superior signal-to-noise ratio than a conventional instrument. We find that poly(Glu), poly(Lys) and alanine-based peptides fold in milliseconds, with longer peptides showing a transient overshoot in helix content.

Synthese und Kristallstrukturen einiger Tetramethylstibonium-Hydrogendicarboxylate / Synthesis and Crystal Structures of Some Tetramethylstibonium Hydrogendicarboxylates

1982 ◽  
Vol 37 (11) ◽  
pp. 1393-1401 ◽  
Author(s):  
Beatrix Milewski-Mahrla ◽  
Hubert Schmidbaur
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Spectroscopic Data ◽  
Molar Ratio ◽  
Ionic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carboxylate Oxygen ◽  
Donor Acceptor ◽  
New Compounds

Reactions of pentamethylantimony (CH3)5Sb with carboxylic acids in the molar ratio 1:2 afford one equivalent of methane and essentially quantitative yields of crystalline tetramothylstibonium hydrogendicarboxylates. Six new compounds of this series have been synthesized using benzoic, o-phthalic, salicylic, 4-ethoxy-salicylic, oxalic, and malic acid, and characterized by analytical and spectroscopic data. An ionic structure with strong hydrogen bonds in the anionic components is proposed.The crystal structures of the hydrogen-dibenzoato (1), hydrogen-ortho-plithalato (2) and 4-ethoxy-hydrogen-salicylate (3) were determined by single crystal X-ray diffraction. The compounds can be described as having ionic lattices with some donor-acceptor inter­actions between the stibonium centers and the carboxylate oxygen atoms. The anions are characterized by strong hydrogen bonds O...H...O. Thus, the (CH3)4Sb-tetrahedron in 1 is distorted by two benzoate oxygon atoms (at 304(2) and 340(2) pin). The cation in 2 is largely undistorted and the anion has a hydrogenphthalate hydrogen bond of d(O...H...O) = 232 pm. The cation-anion contact in 3 is as short as d(Sb-O) = 289 pm rendering the Sb atom pentacoordinate.

Solubility of Iron in Model Systems Containing Organic Acids and Lignin

1992 ◽  
Vol 55 (11) ◽  
pp. 893-898 ◽  
Author(s):  
TAKESHI SUZUKI ◽  
FERGUS M. CLYDESDALE ◽  
TIRA PANDOLF
Keyword(s):  
Ascorbic Acid ◽  
Organic Acids ◽  
Model Systems ◽  
Molar Ratio ◽  
Soluble Form ◽  
Enhancing Effect ◽  
Gastrointestinal Ph ◽  
Soluble Iron ◽  
Ph Values ◽  
Ph Conditions

The effect of six organic acids, ascorbic, citric, fumaric, lactic, malic, and succinic, alone and in combination, at a 1:1.9 molar ratio (Fe+2:ligand) on the solubility of iron was evaluated in the presence of lignin under simulated gastrointestinal pH conditions. The enhancing effect, evaluated under two systems of preparation at two pH values, was in the following order: citric>malic>ascorbic>lactic,fumaric>succinic. Citric acid solubilized 80 and 81% of iron under both pH conditions. When ascorbic acid was mixed with fumaric, lactic, and succinic acids, a higher percentage of soluble iron was retained than with these three acids alone. In the case of citric and malic acids, the addition of ascorbic acid reduced the soluble iron. The percentage of soluble iron obtained when prepared at the endogenous pH (2.5–3.1) was higher than that at pH 5.5. These results indicated that ascorbate bound less iron in a soluble form than citrate or malate but more than fumarate, lactate, or succinate. Also, combinations of citric with malic acid did not demonstrate a synergistic effect.

Zwei neue Bis(trimethylsilyl)aminoderivate des Antimons: MeSb(N{SiMe3}2)2 und MeCl2Sb(N{SiMe3}2)2

1985 ◽  
Vol 40 (7) ◽  
pp. 872-877 ◽  
Author(s):  
W. Kolondra ◽  
W. Schwarz ◽  
J. Weidlein
Keyword(s):  
Raman Spectra ◽  
Structure Determination ◽  
Ir And Raman Spectra ◽  
Molar Ratio ◽  
Monoclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
R Value ◽  
New Compounds ◽  
Ir And Raman

Abstract Unexpectedly the reaction of SbCl3 with Na(N{SiMe3}2) in a 1:3 molar ratio forms MeSb(N{SiMe3}2)2, I, (Me = CH3) and other trimethylsilyl compounds. The colourless and liquid methylstibane derivative I is monomeric in solution and forms MeSbCl2(N{SiMe3}2)2 (II) on reaction with SO2Cl2. Both new compounds have been characterized by analyses, NMR, IR and Raman spectra. The X-ray structure determination for II shows the monoclinic space group P21/C with 4 monomeric units per cell. The structure was refined to an R-value of 0,052.

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