On hydrophobic surfaces

K. Benedek, S. Dong and B. E. Kaiger, Kinetics of unfolding of proteins on hydrophobic surfaces in reversed-phase liquid chiomatography , /. Chromatogr. 317 227-243 (1984). 

With few exceptions it is more efficient and economical to use at least two different pretreatments, i.e. degreasing processes which deal with a) and b), and pickling processes which remove oxide and corrosion films. Degreasing comes first, as pickling processes fail on hydrophobic surfaces. 

Although the detailed mechanism of the longer circulation time of branched PEGylated protein is unclear, the architecture of PEG affects the release profile, the pharmacokinetics of the chug [29], and the behavior of the protein at the interface (e.g., protein absorption on hydrophobic surfaces [30]). 

The thin layers formed in ABS (pH 5.3) always presented a better coverage of the HOPG surface with DNA molecules than layers formed in pH 7.0 PBS [65]. Comparing the thickness and the electrode coverage of the layers obtained with both ss and ds DNA at different pHs on applying a potential of -I- 0.300 V it was concluded that the layer obtained at pH 5.3 presented a self-assembled lattice that was more relaxed and extended on the surface. The results that were obtained by AFM corroborate previous observations that the best binding efficiency of dsDNA on hydrophobic surfaces occurs at approximately pH 5.5 [65]. 

There are numerous studies on the spreading of trisiloxane surfactants on hydrophobic surfaces (for two comprehensive reviews, see [21,22]), but the... 

Rafai S, Sarker D, Bergeron V, Meunier J, Bonn D (2002) Superspreading aqueous sm-factant drops spreading on hydrophobic surfaces. Langmuir 18 10486-10488... 

Wu Y, Rosen MJ (2002) Superspreading of trisiloxane surfactant mixtures on hydrophobic surfaces 2. Interaction and spreading of aqueous trisiloxane surfactant -n-alkyl pyrrolidinone mixtures in contact with polyethylene. Langmuir 18 2205-2215... 

Zhu S, Miller WG, Scriven LE, Davis HT (1994) Superspreading of water-silicone surfactant on hydrophobic surfaces. Colloids Surf A 90 63-78... 

On hydrophobic surfaces, similar effects probably occur and can explain the difference in adsorption of an anionic surfactant in the absence and presence of a nonionic surfactant above the CMC on carbon (78) ... 

From the adsorption-isotherm experiments, it is shown that BPN adsorbs about twenty-times more on hydrophobic quartz than on hydrophilic quartz at 100 ppm. It is also known that BPN autolyzes readily, especially on hydrophobic surfaces (Brode, III, P. F. and Rauch, D. S., The Procter Gamble Company, unpublished results). For the first BPN experiments, the Ge IRE was used directly after cleaning. "Clean" Ge has a water contact angle of about 45°, somewhere between hydrophobic and hydrophilic. To avoid spectral interferences from the Tris buffer bands, the buffer was eliminated from the BPN solutions used for the CIRcle cell experiments. Only CaCl2 (10 mM final concentration) was used to stabilize the BPN against autolysis, and the solution was adjusted to a pH of 8.6 using... 

Wertz CF, Santore MM (1999) Adsorption and relaxation kinetics of albumin and fibrinogen on hydrophobic surfaces single-species and competitive behavior. Langmuir 15(26) 8884-8894... 

In many cases, the adsorption of surfactants on hydrophobic surfaces may follow a Langmuir-type isotherm,... 

Nucleation observed on hydrophobic surface and growth on hydrophilic surface for both A (31-40 and A(31-42. No growth observed for A (31-28... 

Lagaly, G. and I. Dekany. 2005. Adsorption on hydrophobized surfaces Clusters and selforganization. Arfv. Coll. Interface Sci. 114-115 189-204. 

Polymer adsorption has also been adapted to QCM sensing whereby biofunctional thin films are adsorbed on the crystal surface with non-specific binding controlled by tuning of polymer composition. This approach proved successful as applied to carbohydrate-protein interaction by Matsuura et al. through adsorption of lactose bearing amphiphilic polymers on hydrophobic surfaces which then showed RCA12o and peanut lectin (PNA) affinity [33]. Carbohydrate surfaces prepared by photo insertion into an adsorbed polymer were tested by QCM and showed the predicted affinities [34] while in another example a covalently bound glycopolymer demonstrated Concanavalin A detection ability [35]. 

FIGURE 16.17 Schematic of polymeric particle contamination on hydrophobic surface. 

It has been shown that nitrogen occupies a larger area on hydrophobic surfaces than on polar surfaces. The nitrogen molecular area on hydrophobic surfaces is estimated to be between 19 and 22 A [71]. 

For adsorption from water on hydrophobic surfaces, the hydrophobic parts in the molecule attach to the surface with the hydrophUlc part towards the solution. There is no reason for bllayer formation and hence (pseudo-)plateau values are lower than on hydrophilic surfaces. 

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