Keith Mccrea

Hydration of sulphobetaine and tetra(ethylene glycol)-terminated self-assembled monolayers studied by sum frequency generation vibrational spectroscopy.

Sum-frequency generation (SFG) vibrational spectroscopy is used to study the surface and the underlying substrate of both homogeneous and mixed self-assembled monolayers (SAMs) of 11-mercaptoundecyl-1-sulphobetainethiol (HS(CH(2))(11)N(+)(CH(3))(2)(CH(2))(3)SO(3)(-)) and 1-mercapto-11-undecyl tetra(ethylene glycol) (HS(CH(2))(11)O(CH(2)CH(2)O)(4)OH) with an 11-mercapto-1-undecanol (HS(CH(2))(11)OH) diluent. SFG results on the C-H region of the dry and hydrated SAMs gave an in situ look into the molecular orientation and suggested an approach to maximize signal-to-noise ratio on these difficult to analyze hydrophilic SAMs. Vibrational fingerprint studies in the 3000-3600 cm(-1) spectral range for the SAMs exposed serially to air, water, and deuterated water revealed that a layer of tightly bound structured water was associated with the surface of a nonfouling monolayer but was not present on a hydrophobic N-undecylmercaptan (HS(CH(2))(10)CH(3)) control. The percentage of water retained upon submersion in D(2)O correlated well with the relative amount of protein that was previously shown to absorb onto the monolayers. These results provide evidence supporting the current theory regarding the role of a tightly bound vicinal water layer in the protein resistance of a nonfouling group.

Thiophene hydrodesulfurization over bimetallic and promoted nitride catalysts

Alumina-supported bimetallic (Co3Mo3N/Al2O3” and promoted (Co–Mo2N/Al2O3) nitride catalysts have been prepared and characterized. Thiophene hydrodesulfurization (HDS) measurements show that the Co3Mo3N/Al2O3 and Co–Mo2N/Al2O3 catalysts are significantly more active than a Mo2N/Al2O3) catalyst with the same Mo loading. Furthermore, the Co–Mo2N/Al2O3 catalyst has a substantially higher HDS activity than a sulfided Co–MoO3/Al2O3 catalyst with an identical metal loading.

A new optical parametric amplifier based on lithium thioindate used for sum frequency generation vibrational spectroscopic studies of the Amide I mode of an interfacial model peptide

We describe a new optical parametric amplifier (OPA) that employs lithium thioindate, LiInS2 (LIS), to create tunable infrared light between 1500 cm−1 and 2000 cm−1. The OPA based on LIS described within provides intense infrared light with a good beam profile relative to similar OPAs built on silver gallium sulfide, AgGaS2 (AGS), or silver gallium selenide, AgGaSe2 (AGSe). We have used the new LIS OPA to perform surface-specific sum frequency generation (SFG) vibrational spectroscopy of the amide I vibrational mode of a model peptide at the hydrophobic deuterated polystyrene (d8-PS)–phosphate buffered saline interface. This model polypeptide (which is known to be an α-helix in the bulk solution under the high ionic strength conditions employed here) contains hydrophobic leucyl (L) residues and hydrophilic lysyl (K) residues, with sequence Ac-LKKLLKLLKKLLKL-NH2. The amide I mode at the d8-PS-buffer interface was found to be centered around 1655 cm−1. This can be interpreted as the peptide having maintained its α-helical structure when adsorbed on the hydrophobic surface, although other interpretations are discussed.

Cytokines in blood from septic patients interact with surface-immobilized heparin.

When passing blood from septic patients through a column packed with surface heparinized beads, we were able to significantly reduce concentrations of the proinflammatory cytokine tumor necrosis factor (TNF)-&agr; from initially very high levels. Passage of blood over nonheparinized beads did not affect the TNF levels. Meanwhile, concentrations of the regulated on activation, normal T-cells expressed, and secreted leukocyte activating cytokine (RANTES) remained unchanged following passage through the heparinized column, but rose significantly after passage through a column packed with the nonheparinized control beads. We conclude that surface heparinization may be a useful technique for selectively regulating the levels of heparin-binding cytokines from whole blood. This may have potential implications for the treatment of hyper-inflammatory conditions such as severe sepsis. Our data also suggests that surface activation and its associated inflammatory response may be avoided by using heparinization of the extracorporeal circuit.