Liquid-phase sequencer

The appropriate fraction was collected and rechromatographed on the same column with the same gradient but a different ion-pairing reagent (10 mM triethylamine adjusted to pH 6.5 with trifluoroacetic acid). SchistoFLRFamide was isolated on the basis of cross-reactivity to antibodies raised against the molluscan peptide FMRFamide. Sequence analysis was performed with a pulsed-liquid phase sequencer using Edman chemistry (25). 

The primary amino acid sequence of polypeptide is routinely determined using the commercially available gas-liquid-phase sequencers [1, 2] and solid-phase sequencers [3, 4] based on the Mman degradation chemistry [.5j. These instruments can routinely obtain the primary amino acid sequence from 10 to 100 pmol of polypeptide. However, the need for higher sequencing sensitivity remains, as Kent et al. [6] have pointed out that rare proteins may only be present at the 30-300 fmol level on 2D-polyacrylamide gels. 

Baumann, M. (1990). Comparative Gas Phase and Pulsed Liquid Phase Sequencing on a Modified Applied Biosystems 477 A Sequencer, Anal. Biochem. 190 198-208. 

Waterfield M and Bridgen J (1975) Automated liquid phase sequence analysis. In Perham RN (ed.) Instrumentation in Amino Acid Sequence Analysis, pp. 41-71. London Academic Press. 

The Acetaldehyde Oxidation Process. Liquid-phase catalytic oxidation of acetaldehyde (qv) can be directed by appropriate catalysts, such as transition metal salts of cobalt or manganese, to produce anhydride (26). Either ethyl acetate or acetic acid may be used as reaction solvent. The reaction proceeds according to the sequence... 

Benzoic Acid. Ben2oic acid is manufactured from toluene by oxidation in the liquid phase using air and a cobalt catalyst. Typical conditions are 308—790 kPa (30—100 psi) and 130—160°C. The cmde product is purified by distillation, crystallization, or both. Yields are generally >90 mol%, and product purity is generally >99%. Kalama Chemical Company, the largest producer, converts about half of its production to phenol, but most producers consider the most economic process for phenol to be peroxidation of cumene. Other uses of benzoic acid are for the manufacture of benzoyl chloride, of plasticizers such as butyl benzoate, and of sodium benzoate for use in preservatives. In Italy, Snia Viscosa uses benzoic acid as raw material for the production of caprolactam, and subsequendy nylon-6, by the sequence shown below. 

The gas-phase photolysis of 2-furaldehyde in the it -n and ir <-it transitions76 proceeds with fragmentation to CO, furan and C3-hydrocarbons, but a certain amount of resinification is also noted (about 5% quantum yield with excitation of the it - n transition). The latter observation prompted a study of the vacuum liquid-phase photolysis by sunlight or by light from a medium-pressure mercury arc at room temperature24 7S. The resin obtained was submitted to fractionation and structural analysis. On the basis of the results obtained and other mechanistic evidence, the following sequence of events was postulated for the photopolymerization ... 

The novel approach finally taken was to conduct the reaction and purification steps in a reactor-distillation column in which methyl acetate could be made with no additional purification steps and with no unconverted reactant streams. Since the reaction is reversible and equilibrium-limited, high conversion of one reactant can be achieved only with a large excess of the other. However, if the reacting mixture is allowed to flash, the conversion is increased by removal of the methyl acetate from the liquid phase. With the reactants flowing countercurrently in a sequence of... 

The first report on the liquid crystalline properties of these compounds was published by Gray and Mosley [44] in 1976. The series of 4 -n-alkyl-4-cyanobiphenyls (CBn) have been widely studied by different methods due to their readily accessible nematic ranges around room temperature. The compounds have the phase sequences crystal-nematic-isotropic for CBS, CBIO, and monotropic nematic for CBS, CB4 crystal-smectic A-nematic-isotropic for CB9 crystal-smectic A-isotropic for CBll. The lower homologous CB2 is nonmesogenic. The general chemical structure of the compounds CBn is presented in Fig. 1. 

The most common two-dimensional phases in monolayers are the gaseous, liquid-expanded, liquid-condensed, and solid phases. A schematic II-A isotherm is shown in Figure 3 for a fatty acid for the phase sequence gas (G) — G -l- liquid-expanded (LE) — LE — ... 

FIG. 3 An isotherm is depicted for a Langmuir monolayer of an amphiphUe showing the ft-A variation for the phase sequence gas (G) —> G + liquid-expanded (LE) —> LE —> LE + tilted condensed phase (L2) —> L2 —> vertical condensed phase (LS) —> S (solid). Schematic depictions of the molecular organization in the phases are shown above the isotherm. 

Solvent molecules may play a variety of roles in liquid phase reactions. In some cases they merely provide a physical environment in which encounters between reactant molecules take place much as they do in gas phase reactions. Thus they may act merely as space fillers and have negligible influence on the observed reaction rate. At the other extreme, the solvent molecules may act as reactants in the sequence of elementary reactions constituting the mechanism. Although a thorough discussion of these effects would be beyond the scope of this textbook, the paragraphs that follow indicate some important aspects with which the budding ki-neticist should be familiar. 

The following reaction sequence takes place in the liquid phase in a continuous stirred tank reactor. 

Figure 1. Chemical structures of the monomers used in this work. Shown are a) p-phenylene diacrylate (PPDA- melting point 89° C), b) 1,6-hexanediol diacrylate (HDDA- melting point 5° C, boiling point 316° C), and c) C6M, a liquid crystalline diacrylate (phase sequence Isotropic - 116° C -> Nematic -> 86° C - Crystalline.)...

On heating from a crystalline phase, DOBAMBC melts to form a SmC phase, which exists as the thermodynamic minimum structure between 76 and 95°C. At 95°C a thermotropic transition to the SmA phase occurs. Finally, the system clears to the isotropic liquid phase at 117°C. On cooling, the SmC phase supercools into the temperature range where the crystalline solid is more stable (a common occurrence). In fact, at 63°C a new smectic phase (the SmF) appears. This phase is metastable with respect to the crystalline solid such phases are termed monotropic, while thermodynamically stable phases are termed enantiotropic. The kinetic stability of monotropic LC phases is dependent upon purity of the sample and other conditions such as the cooling rate. However, the appearance of monotropic phases is typically reproducible and is often reported in the phase sequence on cooling. It is assumed that phases appearing on heating a sample are enantiotropic. 

Along with the prediction and discovery of a macroscopic dipole in the SmC phase and the invention of ferroelectric liquid crystals in the SSFLC system, the discovery of antiferroelectric liquid crystals stands as a key milestone in chiral smectic LC science. Antiferroelectric switching (see below) was first reported for unichiral 4-[(l-methylheptyloxy)carbonyl]phenyl-4/-octyloxy-4-biphenyl carboxylate [MHPOBC, (3)],16 with structure and phase sequence... 

Figure 8.17 Structure and phase sequence of first banana-phase mesogen, reported by Vorlander in 1929, is given. Liquid crystal phase exhibited by this material (actually Vorlander s original sample) was shown by Pelzl et al.36a to have B6 stmeture, illustrated on right, in 2001. Achiral B6 phase does not switch in response to applied fields in way that can be said to be either ferroelectric or antiferroelectric.

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