PubMed · 4895095
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H L Williams. 1969. The nose as form and function.. https://doi.org/10.1177/000348946907800405
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The behavior of lytic ideally amphipathic peptides of generic composition LiKj(i=2j) and named LKn, n=i+j, is investigated in situ by the monolayer technique combined with the recently developed polarization modulation IR spectroscopy (PMIRRAS). A change in the secondary structure occurs versus peptide length. Peptides longer than 12 residues fold into alpha-helices at interfaces as expected from their design, while enough shorter peptides, from 9 down to 5 residues, form intermolecular antiparallel beta-sheets. Analysis of experimental and calculated PMIRRAS spectra in the amide I and II regions show that peptides are flat oriented at the interfaces. Structures and orientation are preserved whatever the nature of the interface, air/water or DMPC monolayer, and the lateral pressure. Peptide partition constants, KaffPi, are estimated from isobar surface increases of DMPC monolayers. They strongly increase when Pi decreases from 30 mN/m to 8 mN/m and they vary with peptide length with an optimum for 12 residues. This non-monotonous dependence fits with data obtained in bilayers and follows the hemolytic activity of the peptides. Lipid perturbations due to peptide insertion essentially detected on the PO4- and CO bands indicate disorder of the lipid head groups. Lysis induced on membranes by such peptides is proposed to first result from their flat asymmetric insertion.
PURPOSE: To describe a surgical technique to visualize the depth of corneal incisions and lamellar stromal dissections during surgery. METHODS: In porcine cadaver eyes, the aqueous was exchanged by air. Thus an air-to-endothelium interface (i.e., a useful optical surface) was created at the posterior corneal surface. The air-to-endothelium interface was used as a reference plane to visualize the corneal thickness and the relative depth of corneal incisions and dissections. Freehand peripheral corneal incisions, tangential keratotomy incisions, and lamellar stromal dissections were made at an intended corneal depth of 60, 80, and 99%. Light microscopy was used to measure the relative depth of the incisions and dissections. RESULTS: Achieved depth for peripheral corneal incisions averaged 65.2+/-5.3%, 78.8+/-5.1%, and 93.4+/-6.0%, respectively (p<0.05); and for tangential keratotomy incisions, 68.2+/-7.3%, 83.2+/-4.4%, and 95.8+/-3.6%, respectively (p<0.05). Achieved depth for lamellar stromal dissections averaged 58.3+/-9.4%, 81.1+/-3.4%, and 94.4+/-1.5%, respectively (p<0.05). Microperforations occurred with three incisions made at 99% intended depth. CONCLUSION: During surgery, the depth of incisions and lamellar dissections relative to the corneal thickness can be visualized by filling the anterior chamber with air (i.e., by creating an optical interface at the posterior corneal surface).
Nitric oxide, a gaseous free NO radical (.NO) generated in particulate-free gas-phase main-stream smoke of cigarettes, was observed with electrical spin resonance (ESR) using a spin trapping technique. N-Methyl-D-glucamine-dithiocarbamate (MGD)2-Fe2+ complex was used for the NO radical spin trapper in aqueous solution. The intensity of the ESR signal of the spin adduct formed by bubbling smoke from one cigarette increased gradually with time over 2 hours at about 20 degrees C and was constant for 2 days or longer. The time course of the production of the NO radical followed the rate equation y = 1520(1-e-0.018t) for the first-order reaction up to around 25 min after mixing of Fe2+ solution and then slowly approached the maximum value determined by the concentration of the spin adduct. These findings suggest that NO radical is produced slowly from NO radical donors such as amine .NO complexes, peroxinitrite (ONOO-), and other reactants such as nitrogen oxides (NOx), which are produced from the smoke of tobacco leaves, and suggest that its generation could be involved in the decomposition or cleavage of such substances.