Internal Reflection Spectroscopy

Harrick, N. J.; Beckmann, Katrin

doi:10.1007/978-1-4613-4490-2_11

Cited by 720 publications

(1,169 citation statements)

References 14 publications

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“…The lamp used for photolysis was a high pressure Xe arc lamp (Oriel 300 W, Model 6258 OF) equipped with a 10 cm water filter to remove infrared radiation and minimize heating. The depth of penetration of the evanescent wave from the Ge ATR crystal into air was calculated 44 to be 0.13-0.61 mm over the range 4000-860 cm À1 , much greater than the thickness of the SAM (B1.3 nm, measured using ellipsometry). The infrared beam thus interrogates the entire organic monolayer and approximates a spectrum similar to a transmission spectrum.…”

Section: Oh Generationmentioning

confidence: 92%

Reaction of gas phase OH with unsaturated self-assembled monolayers and relevance to atmospheric organic oxidations

Moussa

Finlayson-Pitts

2010

Phys. Chem. Chem. Phys.

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The kinetics and mechanisms of the reaction of gas phase OH radicals with organics on surfaces are of fundamental chemical interest, as well as relevant to understanding the degradation of organics on tropospheric surfaces or when they are components of airborne particles. We report here studies of the oxidation of a terminal alkene self-assembled monolayer (7-octenyltrichlorosilane, C8Q SAM) on a germanium attenuated total reflectance crystal by OH radicals at a concentration of 2.1 Â 10 5 cm À3 at 1 atm total pressure and 298 K in air. Loss of the reactant SAM and the formation of surface products were followed in real time using infrared spectroscopy. From the rate of loss of the CQC bond, a reaction probability within experimental error of unity was derived. The products formed on the surface include organic nitrates and carbonyl compounds, with yields of 10 AE 4% and r7 AE 4%, respectively, and there is evidence for the formation of organic products with C-O bonds such as alcohols, ethers and/or alkyl peroxides and possibly peroxynitrates. The yield of organic nitrates relative to carbonyl compounds is higher than expected based on analogous gas phase mechanisms, suggesting that the branching ratio for the RO 2 + NO reaction is shifted to favor the formation of organic nitrates when the reaction occurs on a surface. Water uptake onto the surface was only slightly enhanced upon oxidation, suggesting that oxidation per se cannot be taken as a predictor of increased hydrophilicity of atmospheric organics. These experiments indicate that the mechanisms for the surface reactions are different from gas phase reactions, but the OH oxidation of surface species will still be a significant contributor to determining their lifetimes in air.

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Section: Oh Generationmentioning

confidence: 92%

Reaction of gas phase OH with unsaturated self-assembled monolayers and relevance to atmospheric organic oxidations

Moussa

Finlayson-Pitts

2010

Phys. Chem. Chem. Phys.

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“…After an early experimental work 54 with a manual/nonscanning spectrometer, an interesting application appeared using a liquid medium with the refractive index matching that of the powder. 55 The CD in the low UV of immobilized enzymes on silica gel particles (tens to hundreds of microns large) has been the subject of a well detailed article, 56 with the aim to obtain secondary structure estimates, with use of short path cells close to the photomultiplier tube surface, to minimize scattering effects.…”

Section: Liquid Suspensionsmentioning

confidence: 99%

Experimental aspects of solid state circular dichroism

2009

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“…The parameters O x , O y and O z are the electric ¢eld components. Because the thickness of the ¢lm was estimated as being more than 20 Wm, whereas the amplitude of the evanescent wave decays (at 1/O of its initial value) after 1 Wm in a germanium plate, the values for these components are those given by [22] according to a thick-¢lm approximation. The contribution of S lipid to S helix was taken into account and the helix tilt L was calculated from S helix H S helix H S helix S lipid according to…”

Section: Analysis Of Atr^ftir Datamentioning

confidence: 99%

The orientation of the antibiotic peptide maculatin 1.1 in DMPG and DMPC lipid bilayers. Support for a pore‐forming mechanism

et al. 2002

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Maculatin 1.1 is an antimicrobial peptide isolated from the Australian tree frog Litoria genimaculata that adopts an amphipathic, K K-helical structure in solution. Its orientation and conformation when incorporated to pre-formed DMPG (1,2-dimyristoyl-sn-glycero-3-phosphoglycerol) and DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) vesicles was determined using polarised Fourier transform infrared^attenuated total reflection infrared and deuterium exchange experiments. For DMPG membranes, our results show insertion of V V70% of the maculatin 1.1 molecules, with an angle of insertion of approximately 35³ to the membrane normal and with a predominant K K-helical structure. These results suggest that maculatin 1.1 acts through a pore-forming mechanism to lyse bacterial membranes. A similar degree of insertion in DMPG (65%) and K K-helical structure was observed for a biologically inactive, less amphipathic maculatin 1.1 analogue, P15A, although the helix tilt was found to be greater (46³) than for maculatin 1.1. Similar experiments performed using DMPC liposomes showed poor insertion, less than 5%, for both maculatin 1.1 and its analogue. In addition, the shape of the amide I band in these samples is consistent with K K-helix, L L-structure and disordered structures being present in similar proportion. These results clearly show that maculatin 1.1 inserts preferentially in negatively charged membranes (DMPG) which mimic the negatively charged membrane of Gram-positive bacteria. We attribute the high percentage of insertion of the biologically inactive analogue in DMPG to the fact that its concentration on the membrane surface in our experiments is likely to be much higher than that found in physiological conditions. ß 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

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Internal Reflection Spectroscopy

Cited by 720 publications

References 14 publications

Reaction of gas phase OH with unsaturated self-assembled monolayers and relevance to atmospheric organic oxidations

Reaction of gas phase OH with unsaturated self-assembled monolayers and relevance to atmospheric organic oxidations

Experimental aspects of solid state circular dichroism

The orientation of the antibiotic peptide maculatin 1.1 in DMPG and DMPC lipid bilayers. Support for a pore‐forming mechanism

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