Microcalorimetric Evidence of Hydrophobic Interactions between Hydrophobically Modified Cationic Polysaccharides and Surfactants of the Same Charge

2007 ◽  
Vol 111 (39) ◽  
pp. 11453-11462 ◽  
Author(s):  
Guangyue Bai ◽  
José A. M. Catita ◽  
Marieta Nichifor ◽  
Margarida Bastos
Keyword(s):  
Hydrophobic Interactions ◽  
Hydrophobically Modified

Hydrophobic Interactions of Poly(N-isopropylacrylamide) with Hydrophobically Modified Poly(sodium acrylate) in Aqueous Solution

1997 ◽  
Vol 30 (26) ◽  
pp. 8293-8297 ◽  
Author(s):  
G. Bokias ◽  
D. Hourdet ◽  
I. Iliopoulos ◽  
G. Staikos ◽  
R. Audebert
Keyword(s):  
Aqueous Solution ◽  
Hydrophobic Interactions ◽  
Sodium Acrylate ◽  
Hydrophobically Modified

Influence of Weak Hydrophobic Interactions on in Situ Viscosity of a Hydrophobically Modified Water-Soluble Polymer

2017 ◽  
Vol 32 (1) ◽  
pp. 89-98 ◽  
Author(s):  
Alette Løbø Viken ◽  
Kristine Spildo ◽  
Roland Reichenbach-Klinke ◽  
Ketil Djurhuus ◽  
Tormod Skauge
Keyword(s):  
Hydrophobic Interactions ◽  
Water Soluble ◽  
Soluble Polymer ◽  
Water Soluble Polymer ◽  
Hydrophobically Modified

scholarly journals Rheological Properties in Aqueous Solution for Hydrophobically Modified Polyacrylamides Prepared in Inverse Emulsion Polymerization

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Shirley Carro ◽  
Valeria J. Gonzalez-Coronel ◽  
Jorge Castillo-Tejas ◽  
Hortensia Maldonado-Textle ◽  
Nancy Tepale
Keyword(s):  
Emulsion Polymerization ◽  
Shear Viscosity ◽  
Hydrophobic Interactions ◽  
Monomer Concentration ◽  
Feed Composition ◽  
Inverse Emulsion Polymerization ◽  
Inverse Emulsion ◽  
Hydrophobically Modified ◽  
Initial Monomer ◽  
Modified Polyacrylamide

Inverse emulsion polymerization technique was employed to synthesize hydrophobically modified polyacrylamide polymers with hydrophobe contents near to feed composition. Three different structures were obtained: multisticker, telechelic, and combined. N-Dimethyl-acrylamide (DMAM), n-dodecylacrylamide (DAM), and n-hexadecylacrylamide (HDAM) were used as hydrophobic comonomers. The effect of the hydrophobe length of comonomer, the initial monomer, and surfactant concentrations on shear viscosity was studied. Results show that the molecular weight of copolymer increases with initial monomer concentration and by increasing emulsifier concentration it remained almost constant. Shear viscosity measurements results show that the length of the hydrophobic comonomer augments the hydrophobic interactions causing an increase in viscosity and that the polymer thickening ability is higher for combined polymers.

Molecular dynamics study on the interaction between doxorubicin and hydrophobically modified chitosan oligosaccharide

RSC Advances ◽  
2014 ◽  
Vol 4 (45) ◽  
pp. 23730-23739 ◽  
Author(s):  
Peng Shan ◽  
Jia-Wei Shen ◽  
Dong-Hang Xu ◽  
Li-Yun Shi ◽  
Jie Gao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Hydrophobic Interactions ◽  
Chitosan Oligosaccharide ◽  
Π Interactions ◽  
Modified Chitosan ◽  
Chitosan Oligosaccharides ◽  
Hydrophobically Modified

Both π–π interactions and hydrophobic interactions were found to be essential for the loading of doxorubicin on hydrophobically modified chitosan oligosaccharides.

Influence of Polymer Charge, Temperature, and Surfactants on Surface Sizing of Liner and Greaseproof Paper With Hydrophobically Modified Starch

TAPPI Journal ◽  
2009 ◽  
Vol 8 (2) ◽  
pp. 33-38 ◽  
Author(s):  
ANNA JONHED ◽  
LARS JÄRNSTRÖM
Keyword(s):  
Phase Separation ◽  
Contact Angles ◽  
Low Ph ◽  
Hydrophobically Modified ◽  
Paper Sizing ◽  
Surface Sizing ◽  
Separation Temperature ◽  
Hydrophobic Nature ◽  
Sizing Agents ◽  
Charge Temperature

The aim of this study was to investigate the properties of hydrophobically modified (HM) quaterna-ry ammonium starch ethers for paper sizing. These starches possess temperature-responsive properties; that is, gelation or phase separation occurs at a certain temperature upon cooling. This insolubility of the HM starches in water at room temperature improved their performance as sizing agents. The contact angles for water on sized liner were substantially larger than on unsized liner. When the application temperature was well above the critical phase-separation temperature, larger contact angles were obtained for liner independently of pH compared with those at the lower application temperature. Cobb60 values for liner decreased upon surface sizing, with a low pH and high application temperature giving lower water penetration. Contact angles on greaseproof paper decreased upon sur-face sizing as compared to unsized greaseproof paper, independently of pH and temperature. Greaseproof paper showed no great difference between unsized substrates and substrates sized with HM starch at different pH. This is probably due to the already hydrophobic nature of greaseproof paper. However, the Cobb60 values increased at low pH and low application temperature. Surfactants were added to investigate how they affect the sized surface. Addition of surfactant reduces the contact angles, in spite of indications of complex formation.

Controlling porosity and density of nanocellulose aerogels for superhydrophobic light materials

TAPPI Journal ◽  
2018 ◽  
Vol 17 (03) ◽  
pp. 145-153 ◽  
Author(s):  
Chengua Yu ◽  
Feng Wang ◽  
Shiyu Fu ◽  
Lucian Lucia
Keyword(s):  
Contact Angle ◽  
Freeze Drying ◽  
Engine Oil ◽  
High Porosity ◽  
Water Mixture ◽  
Waste Engine Oil ◽  
Hydrophobically Modified ◽  
Static Contact ◽  
Oil Water ◽  
Hydrophobic Material

A very low-density oil-absorbing hydrophobic material was fabricated from cellulose nanofiber aerogels–coated silane substances. Nanocellulose aerogels (NCA) superabsorbents were prepared by freeze drying cellulose nanofibril dispersions at 0.2%, 0.5%, 0.8%, 1.0%, and 1.5% w/w. The NCA were hydrophobically modified with methyltrimethoxysilane. The surface morphology and wettability were characterized by scanning electron microscopy and static contact angle. The aerogels displayed an ultralow density (2.0–16.7 mg·cm-3), high porosity (99.9%–98.9%), and superhydrophobicity as evidenced by the contact angle of ~150° that enabled the aerogels to effectively absorb oil from an oil/water mixture. The absorption capacities of hydrophobic nanocellulose aerogels for waste engine oil and olive oil could be up to 140 g·g-1 and 179.1 g·g-1, respectively.

Molecular Basis of Iterative C–H Oxidation by TamI, a Multifunctional P450 Monooxygenase from the Tirandamycin Biosynthetic Pathway

2020 ◽  
Author(s):  
Sean A. Newmister ◽  
Kinshuk Raj Srivastava ◽  
Rosa V. Espinoza ◽  
Kersti Caddell Haatveit ◽  
Yogan Khatri ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Molecular Basis ◽  
Hydrophobic Interactions ◽  
Cytochromes P450 ◽  
Targeted Mutagenesis ◽  
P450 Monooxygenase ◽  
Bond Functionalization ◽  
Dynamics Simulations

Biocatalysis offers an expanding and powerful strategy to construct and diversify complex molecules by C-H bond functionalization. Due to their high selectivity, enzymes have become an essential tool for C-H bond functionalization and offer complementary reactivity to small-molecule catalysts. Hemoproteins, particularly cytochromes P450, have proven effective for selective oxidation of unactivated C-H bonds. Previously, we reported the in vitro characterization of an oxidative tailoring cascade in which TamI, a multifunctional P450 functions co-dependently with the TamL flavoprotein to catalyze regio- and stereoselective hydroxylations and epoxidation to yield tirandamycin A and tirandamycin B. TamI follows a defined order including 1) C10 hydroxylation, 2) C11/C12 epoxidation, and 3) C18 hydroxylation. Here we present a structural, biochemical, and computational investigation of TamI to understand the molecular basis of its substrate binding, diverse reactivity, and specific reaction sequence. The crystal structure of TamI in complex with tirandamycin C together with molecular dynamics simulations and targeted mutagenesis suggest that hydrophobic interactions with the polyene chain of its natural substrate are critical for molecular recognition. QM/MM calculations and molecular dynamics simulations of TamI with variant substrates provided detailed information on the molecular basis of sequential reactivity, and pattern of regio- and stereo-selectivity in catalyzing the three-step oxidative cascade.<br>

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