In gel phase

Cesaro, A., Cuppo, F., Fabri, D., Sussich, F. (1999). Thermodynamic behaviour of mixed biopolymers in solution and in gel phase. Thermochimica Acta, 328, 143-153. 

Notwithstanding all its advantages, the principle of solid-phase synthesis cannot be applied to all kinds of chemical reactions. Although reactants are used in excess, reaction is not always quantitative. The resulting impurities cannot be separated on the solid phase, giving rise to separation problems particularly in multi-step systems. Moreover, only limited use can often be made of conventional analytical methods (NMR, MS). Recent methods of 13C-NMR spectroscopy on solid phases [21] or in gel phases [22] are ideally suited for solid-phase synthesis, but are not universally available owing to the expensive instrumentation. 

If there is some molecular motion with characteristic times on the order of ICT sec, the NMR spectrum will no longer have the Pake doublet lineshape discussed earlier. For example, in gel-phase bilayers a perdeuterated lipid acyl chain will have a broad, relatively featureless spectmm, as shown in Fig. 3. These spectra do not lend themselves to easy analysis The molecular motion in the membrane is not rapid enough to be axially symmetric (see the description of the fluid bilayer below) on the NMR time scale but is fast enough to influence the average value of the quadrupolar interaction and thus the splittings of the individual labels. 

The transition from liquid-crystalline to gel phase, which results in a marked change in the physical properties of the lipid bilayer, also strongly affects the activities of membrane proteins. Some membrane proteins, such as the Ca +-ATPase, show low activity in gel-phase bilayers because of the effects of the gel phase on the protein conformation (22). An increase in the bilayer thickness during a liquid-crystalline-gel transition has been shown also to affect the activity of membrane proteins, for example, that of the diacylglycerol kinase (18). 

Cholesterol affects a large variety of membrane properties in animal cells (39). It is involved in modifying dynamical membrane properties by reducing passive permeation, slowing down the lateral diffusion of molecules in fluid-like membranes, and speeding up diffusion in gel-phase membranes. It also affects bilayer properties by condensing the bilayer, which changes its elastic properties and promotes the order of phospholipid acyl chains in the hydrophobic membrane core. In this manner, cholesterol develops the formation of the liquid-ordered... 

Mishima, K. Satoh, K. Ogihara, T. Optical birefringence of phosphatidylcholine liposomes in gel phases. Biochim. Biophys. Acta 1977, 898, 231-238. 

A further development in gel-phase C NMR spectroscopic analysis has been the use of " C enriched building blocks in the synthesis [114]. This allows the use of much smaller quantities of resin (—20 mg) containing less than 1 mg of the moiety to be analysed. In the case of synthesis on a Tentagel resin, rapid analysis is possible because of the enhanced mobility of the system and the reduced number of transients that need to be accumulated. 

Figure 2. A snapshot of the molecular dynamics unit cell that consists of 32 DLPE molecules in gel phase and 362 water molecules. For clarity the water molecules are not displayed in the figure.

Because our simulations were performed on a rather small sample and only for 96 ps, it is possible that we did not sample enough of the configuration space of the system. To avoid some of the effects due to this problem we performed another 96-ps simulation (simulation C) in which the phospholipid molecules were again kept in gel phase, but were initially prepared in a different configuration. The symmetrized polarization profile obtained from... 

Spinning at 54.7° (the magic angle) from static field axis to achieve averaging of the chemical shift anisotropy to zero. This sharpens the signals of soMd state spectra to solution-state-Mke widths. Suppression of C dipolar couplings is also achieved. Also used in gel-phase NMR (e.g. beads) and in NMR of tissue samples. 

Brandstetter, M. (2009). Ultrasonically enhanced in-line Attenuated Total Reflection (ATR) infrared absorption spectroscopy of suspensions. Diploma Thesis, Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna Braunshier, C. Hametner, C. Froehlich, J. Schnoeller, J. Hutter, H. (2008). Novel monodisperse PEG-grafted polystyrene resins synthesis and application in gel-phase 13C NMR spectroscopy. Tetrahedron Letters Vol.49, pp. 7103-7105, ISSN 0040-4039... 

Fig. 4. The stepwise peptide synthesis in gel phase with polymer-supported active esters of amino acids, a model of the protein biosynthesis...

Fig. 8.1 Order parameters from last 5 ns of the simulations of peptides and four types of lipid bilayers. Lipids are separated into two sliees around peptide nearer to the peptide and more influ-eneed as si and farther, less influeneed, as s2. In gel phase peptide causes disorder by its presence. In PC phase most of peptides relatively keep properties of pure lipid. Only increases order in membrane. However more fluetuating peptides disorder membrane in the middle...

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