Lipid crystallization measurements

In another set of experiments, the integrated electron densities in the region of the DPPE lipid monolayer measured by GIXD before and after S-layer crystallization B. coagulans E38/vl and B. sphaericus CCM 2177) have been compared. The electron densi-... 

Conductivity, in water activity measurement, 67-70 Confocal laser scanning microscopy to characterize lipid crystals, 575-579 description of, 575, 577 Conjugated dienes and trienes, determination of, 515-517 Conjugated linoleic acid (CLA), fatty acid analysis, 437-438, 445-446 Convection oven, gravimetric measurement of water, 7-8, 10-11... 

Development and Use of a Novel Technique to Measure Exchange Between Lipid Crystals and Oils... 

Technique to Measure Lipid Crystals/Oils Exchange... 

Lipid Crystals. Tripalmitin (>99% pure) (PPP obtained from Sigma Chemical Co., Stockholm, Sweden) was used. Crystals were recrystallized in hexane to give well-characterized 3-crystals. Hieir surface area was measured by Brunauer, Emmett, and Teller analysis to be 2.077 mVg. 

The primary product of the hot homogenization is a nanoemulsion resulting from the liquid state of the lipid. Solid particles are expected to be formed by the cooling of the sample to room temperature or below. Because of the small particle size and the presence of the emulsifiers, lipid crystallization may be highly retarded, and the sample may remain as a supercooled melt (nanoemulsion) for several months [28], Westesen and Bunjes found that purported SLN data published by another group were, in fact, measurements from supercooled melts [29],... 

However, despite this progress, it is highly recommended that both PCS and LD be used simultaneously. It should be kept in mind that both methods are not measuring particle sizes. Rather, they detect light-scattering effects that are used to calculate particle size. For example, uncertainties may result from nonspherical particle shapes and from the assumption of certain parameters that are used to calculate the particle size. Platelet structures commonly occur during lipid crystallization [57] and have also been observed for SLN [11,40,58], The presence of several populations and other colloidal structures adds further difficulties. 

The parameters K1/ K2/ and K3 are defined by the refractive indices of the crystal and sample and by the incidence angle [32]. If the sample has uniaxial symmetry, only two polarized spectra are necessary to characterize the orientation. If the optical axis is along the plane of the sample, such as for stretched polymer films, only the two s-polarized spectra are needed to determine kz and kx. These are then used to calculate a dichroic ratio or a P2) value with Equation (25) (replacing absorbance with absorption index). In contrast, a uniaxial sample with its optical axis perpendicular to the crystal surface requires the acquisition of spectra with both p- and s-polarizations, but the Z- and X-axes are now equivalent. This approach was used, through dichroic ratio measurements, to monitor the orientation of polymer chains at various depths during the drying of latex [33]. This type of symmetry is often encountered in non-polymeric samples, for instance, in ultrathin films of lipids or self-assembled monolayers. 

Membrane integral proteins have transmembrane domains that insert directly into lipid bilayers. Transmembrane domains (TMDs) consist predominantly of nonpolar amino acid residues and may traverse the bilayer once or several times. High-resolution structural information is available for only a few integral membrane proteins, primarily because it is difficult to obtain membrane protein crystals that are adequate for X-ray diffraction measurements. 

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