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Trace amounts of poly[(R)‐3‐hydroxybutanoate] were isolated from competent Escherichia coli, spinach, bovine serum albumin, beef heart mitochondria, and aortal tissues, all sources in which it is not accumulated as storage material. Its identity was in all cases proved by 1H‐NMR spectroscopy. In some runs, the poly[(R)‐3‐hydroxybutanoate] isolated from competent E. coli also contained some 3‐hydroxyvalerate, an observation confirmed by 1H‐NMR spectroscopy and gas chromatography. The absolute configuration of the polymers isolated from E. coli and spinach was shown to be (all‐R) by gas chromatography on chiral columns.

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Phase equilibrium, glass-forming, properties and structure of the glasses in the TeO2--B203 system have been investigated. The phase diagram is a simple eutectic-like type without any compound formation. A wide region of stable phase separation has been established. A monotectic temperature at 934 K and nonvariant point at 73.6% TeO2 has been determined. The temperature dependence of the stable phase separation in the system has been studied. Some properties (density, transformation temperature, softening point, coefficient of thermal expansion, hardness, absorption in the UV and VIS region) of the tellurite borate glasses have been investigated. A structural interpretation of the glasses, on the basis of B 11 NMR spectra was undertaken and two coordination states of boron atoms have been established. A simple model of two telluriumboron-oxygen building units is presented.

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Neutron and x-ray diffraction experiments of high resolving power with neutrons from a spallation source and high-energy photons from a synchrotron have been performed on compositional series of binary tellurite glasses with additions of K 2 O or P 2 O 5 (max. 16 or 32 mol%). Since the P-O bond lengths do not interfere with the Te-O peaks the Te-O and O-O correlations are approximated by Gaussian fitting of the x-ray and neutron correlation functions up to lengths of 0.28 nm. In the case of K 2 O-TeO 2 glasses reasonable assumptions are made for the K-O first-neighbour peaks. Te-O and O-O coordination numbers are four and five for the glasses of compositions close to pure TeO 2 which indicates formation of a three-dimensional network of cornerconnected TeO 4 trigonal bipyramids. The tellurite network groups are TeO 4 and TeO 3 units in K 2 O-TeO 2 glasses and TeO 4 and TeO 5 units in P 2 O 5 -TeO 2 glasses. Additional Te-O neighbours found at 0.23 nm < r < 0.26 nm for K 2 O-TeO 2 glasses suggest the existence of TeO 3+1 units and those found at 0.23 nm < r < 0.29 nm for the P 2 O 5 -TeO 2 glasses indicate the existence of distorted TeO 6 polyhedra. Tellurite networks are flexible to form the appropriate coordination environments for quite different ions or groups of opposite charge such as K + ions and (PO 4/2 ) − tetrahedra where change of the TeO n network units provides the needed number of oxygen neighbours.

Repetitive treatment of the biopolymer P(3-HB) (molecular weight > lo5 Dalton, storuge OJ s-P(3-HB)), with lithium hexamethyl disilazanid (LHMDS) at -70" in THF leads to a mixture of oligomers with increasingly sharp distribution around a 15-, 30-, and 45mer. Discrete fragments are also isolated when P(3-HB) is heated under reflux (89O) in neat Et,N. Linear oligo(3-HB) derivatives (3-7) containing up to 96 3-HB units are synthesized using an exponential segment-coupling strategy. These oligomers are used to calibrate size-exclusion chromatography columns for the analysis of oligo(3-HB) samples from the different sources. The linear oligo-(3-HB) derivatives also served as a model with respect to the physical properties ofhigh molecular weight P(3-HB) and were investigated as such by transmission electron microscopy (TEM) and by small-and wide-angle X-ray scattering (SAXS and WAXS). The thicknesses of the lamellar crystallites (long periods) formed by the Rmer, 16mer, and 32mer, are ca.26, 52, and 53 A, respectively, indicating that the 32mer molecules are folded once, very tightly, into a 'hair-pin'-type conformation. High-molecular-weight P(3-HB). which was crystallized in a similar way, also has a lamellar crystallite thickness of ca. [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65] A. Thus, the treatment of P(3-HB) with LHMDS at low temperature causes etching of the amorphous regions, an effect well known in polymer science for studying the regularity of chain folding. The ca. 50-A packing within the tight folds of P(3-HB) is discussed in view of its possible function in ion transport through cell membranes.Polyhydroxybutyrate (P(3-HB)) is the prototype of a class of biopolymers [I] [2] called polyhydroxyalkanoates (PHA; for review articles, see . They are used by microorganisms as a means to store energy and reductase equivalents and as a carbon source (high-molecular-weight s-P(3-HB), > lo5 Dalton). A copolymer of P(3-HB) and P(3-HV) (V = valerate) is produced by fermentation and sold as a biodegradable and biocompatible plastic material under the trade name BZOPOL [6]. Low-molecular-weight P(3-HB) (100-200 units) was found in the membranes of prokaryotic and eukaryotic cells. It forms complexes, for instance, with calcium polyphosphate and albumin (c-P(3-HB)) [7]. The structure and function of c-P(3-HB) are greatly in debate, concerning suggestions including stabilizing proteins to a Ca2+ polyphosphate (PPi), and acting as a DNA channel through lipid membranes [7]. We have embarked on an investigation to obtain information on the structure and properties of oligo(3-HB) derivatives [3].

C(102) to C(l05)l were refined anisotropically. Bonds o f the disordered THF were constrained during refinements. No attempts were made to locate the H atoms. The final refinement of 1 converged at R = 0.053, UR = 0.081, and COF = 2.78 for observed reflections. The maximum and minimum residual electron densities are 0.94 and -0.85 ejA', respectively.