Isotopes, wool, and rangeland monitoring: Let the sheep do the sampling

Stable carbon isotope analyses of wool staples provided insight into the vegetation consumed by sheep at a temporal resolution not previously studied. Contemporary Australian and historic South African samples dating back to 1916 were analyzed for their stable carbon isotope ratio, a proxy for the proportion of C-3 and C-4 plant species consumed by animals. Sheep sample vegetation continuously throughout a year, and as their wool grows it integrates and stores information about their diet. In subtropical and tropical rangelands the majority of grass species are C-4. Since sheep prefer to graze, and their wool is an isotopic record of their diet, we now have the potential to develop a high resolution index to the availability of grass from a sheep's perspective. Isotopic analyses of wool suggest a new direction for monitoring grazing and for the reconstruction of past vegetation changes, which will make a significant contribution to traditional rangeland ecology and management. It is recommended that isotopic and other analyses of wool be further developed for use in rangeland monitoring programs to provide valuable feedback for land managers.

DNA packaging by L1 and L2 capsid proteins of bovine papillomavirus type 1

Encapsidation of circular DNA by papillomavirus capsid protein was investigated in Cos-1 cells. Plasmids carrying both an SV40 origin of replication (or) and an E. coli on were introduced into Cos-1 cells by DNA transfection. PV capsid proteins were supplied in trans by recombinant vaccinia viruses. Pseudovirions were purified from infected cells and their packaged DNA was extracted and used to transform E. coil as an indication of packaging efficacy. VLPs assembled from BPV-1 L1 alone packaged little plasmid DNA, whereas VLPs assembled from BPV-1 L1+L2 packaged plasmid DNA at least 50 times more effectively. BPV-1 L1+L2 VLPs packaged a plasmid containing BPV-1 sequence 8.2 +/- 3.1 times more effectively than a plasmid without BW sequences. Using a series of plasmid constructs comprising a core BPV-1 sequence and spacer DNA it was demonstrated that BW VLPs could accommodate a maximum of about 10.2 kb of plasmid DNA, and that longer closed circular DNA was truncated to produce less dense virions with shorter plasmid sequences. The present study suggests that packaging of genome within PV virions involves interaction of L2 protein with specific DNA sequences, and demonstrates that PV pseudovirions have the potential to be used as DNA delivery vectors for plasmids of up to 10.2 kb. (C) 1998 Academic Press.

Carrageenans from Australian representatives of the family Cystocloniaceae (Gigartinales, Rhodophyta), with description of Calliblepharis celatospora sp. nov., and transfer of Austroclonium to the family Areschougiaceae

Ten Australian representatives from seven of the 10 genera presently constituting the family Cystolcloniaceae have been analyzed for their cell-wall galactans. Included in our survey are the monotypic Australian-endemic genera Austroclonium, Gloiophyllis, Erythronaema, and Stictosporum, one species of Craspedocarpus, three species of Rhodophyllis, and two species of Calliblepharis. As one of the species of the latter genus is endemic to Western Australia and presently undescribed, we illustrate its habit and anatomical features in formally proposing to name it Calliblepharis celatospora Kraft, sp. nov. All the species surveyed essentially produce typical iota (iota)-carrageenans, with the exception of Austroclonium. The sulfated galactans from Austroclonium predominantly contain the repeating units of iota-, alpha (alpha)-, and 6'-O-methylated iota- and alpha-carrageenans; whether these exist as discrete polysaccharides or a complex hybrid structure was not resolved. Thus, Austroclonium carrageenans resemble the polysaccharides from Rhabdonia, Areschougia, and Erythroclonium. Although these latter three genera are currently included in the large gigartinalean family Solieriaceae, all produce significantly different carrageenans from Solieria itself and related genera such as Eucheuma, Kappaphycus, Betaphycus, Sarcodiotheca, Agardhiella, Sarconema, and Callophycus. In consideration of these findings, as well as of significant anatomical similarities, we provisionally recommend reestablishment of the family Rhabdoniaceae Kylin (as the family Areschougiaceae J. Agardh) for Rhabdonia, Areschougia, Erythroclonium, and Austroclonium.

Thermochromism and structure of piperazinium tetrachlorocuprate(II) complexes

The tetrachlorocuprate(II) ion can crystallize in two different structures with the piperazinium dication (pipzH(2)). Both structures contain discrete CuCl42- species. A yellow compound (pipzH(2))[CuCl4]. 2H(2)O (1) is monoclinic (C2/c, Z = 4, a = 10.538(3) Angstrom, b = 7.4312(5) Angstrom, c = 17.281(4) Angstrom, beta = 111.900(10)degrees) and contains the CuCl42- ion as a distorted tetrahedron. A green compound (pipzH(2))(2)[CuCl4]. Cl-2. 3H(2)O (2) is triclinic (P (1) over bar, Z = 2, a = 9.264(3) Angstrom, b = 10.447(2) Angstrom, c = 11.366(2) Angstrom, alpha = 68.38 degrees, beta = 82.86(2)degrees, gamma = 83.05(2)degrees) and contains the CuCl42- ion with a square planar geometry. This latter compound shows thermo/photochromism, changing from green to yellow upon heating or laser irradiation.

Nest temperature and respiratory gases during natural incubation in the broad-shelled river turtle, Chelodina expansa (Testudinata : Chelidae)

Temperature was monitored in three natural nests, and oxygen and carbon dioxide partial pressure monitored in one natural nest of the broad-shelled river turtle, Chelodina expansa, throughout incubation. Nest temperature decreased after nest construction in autumn, remained low during winter and gradually increased in spring to a maximum in summer. In a nest where temperature was recorded every hour, temperature typically fluctuated through a 2 degrees C cycle on a daily basis throughout the entire incubation period, and the nest always heated faster than it cooled. Oxygen and carbon dioxide partial pressures in this nest were similar to soil oxygen and carbon dioxide partial pressures for the first 5 months of incubation, but nest respiratory gas tensions deviated from the surrounding soil over the last three months of incubation. Nest respiratory gas tensions were not greatly different from those in the atmosphere above the ground except after periods of rain. After heavy rain during the last 3 months of incubation the nest became moderately hypoxic (P-O2 similar to 100 Torr) and hypercapnic (P-CO2 similar to 50 Torr) for several successive days. These short periods of hypoxia and hypercapnia were not lethal.

Aminotriazines as locking fragments in macrocyclic synthesis

The macrocyclic compounds (6-(4',6'-diamino-1',3',5'-triazinyl)-1,4,6,8,11-pentaazacyclotetradecane)copper(II) triperchlorate dihydrate, [Cu(HL2)](ClO4)(3). 2H(2)O, (6-(6'-amino-4'-oxo-1'H-1',3',5'-triazinyl)-1,4,6,8,11-pentaazacyclotetradecane)copper(II) diperchlorate hydrate, [CuL3](ClO4)(2). H2O, and [(6-(4',6'-dioxo-1'H-1',3',5'-triazinyl) 1,4,6,8,11-pentaazacyclotetradecane)copper(II)] diperchlorate, [CuL4](ClO4)(2), have been synthesized. The macrocycles synthesized contain respectively pendant melamine, ammeline,and ammelide rings. The X-ray cyrstallographic analyses of [Cu(HL2)](ClO4)(3). 2H(2)O, triclinic, space group P (1) over bar, a = 9.489(10) Angstrom, b = 12.340(2) Angstrom, c = 24.496(4) Angstrom, alpha = 87.74(10)degrees beta = 85.51(10)degrees gamma = 70.95(10)degrees and Z = 4, and {[CuL3](ClO4)(2). H2O}2, monoclinic, space group C2/c, a = 18.624(8) Angstrom, b = 17.160(2) Angstrom, c = 15.998(6) Angstrom, beta = 117.82(2)degrees, and Z = 4, are reported. The structure of [Cu(HL2)](ClO4)(3). 2H(2)O shows the formation of linear tapes, formed by a combination of hydrogen bonds and pi-pi stacking interactions. The structure of [CuL3](ClO4)(2). H2O displays formation of dimers, formed by a coordinate bond from the oxygen in one molecule to the copper atom of another. The tautomeric forms of the ammeline and ammelide moieties have been determined. The potential of these compounds as subunits for cocrystallization has been investigated.

Determination of chemical shielding tensor of an indole carbon and application of tryptophan orientation of a membrane peptide

Using tryptophan C-13-enriched at the C-4 (C epsilon(3)) of the indole, the orientation of the C epsilon(3) chemical shift tensor relative to the C epsilon(3)-H dipolar axis was determined from the C-13 chemical shift/C-13-H-1 dipolar 2D NMR powder pattern. The principal values obtained were 208, 137 and 15 ppm with sigma(33) perpendicular to the indole plane, and sigma(11) (least shielded direction) 5 degrees off the C epsilon(3)-H bond toward C xi(3). The side off the C epsilon(3)-H bond was determined by comparing the reduced chemical shift anisotropies obtained by solid-state NMR and from molecular dynamics calculations of [4-C-13] tryptophans in gramicidin A aligned in phospholipid membranes. (C) 1999 Elsevier Science B.V. All rights reserved.

Carbon structure and porosity of carbonaceous adsorbents in relation to their adsorption properties

A number of carbonaceous adsorbents were prepared by carbonisation at 600 degrees C following acidic oxidation under various conditions. Effects of the chemical nature of the precursor, such as the ratio of aromatic to aliphatic carbons and oxygen content, on the chemical and structural characteristics of the resultant chars were investigated using C-13 NMR and Raman spectroscopy, respectively. The C-13 NMR spectral parameters of the coal samples show that as the severity of oxidation conditions increased, the ratio of aromatic to aliphatic carbons increased. Furthermore, it was also found that the amount of disorganised carbon affects both the pore structure and the adsorption properties of carbonaceous adsorbents. It is demonstrated that higher amount of the disorganised carbon indicates smaller micropore size. (C) 1999 Elsevier Science Ltd. All rights reserved.

Climate change, coral bleaching and the future of the world's coral reefs

Sea temperatures in many tropical regions have increased by almost 1 degrees C over the past 100 years, and are currently increasing at similar to 1-2 degrees C per century. Coral bleaching occurs when the thermal tolerance of corals and their photosynthetic symbionts (zooxanthellae) is exceeded. Mass coral bleaching has occurred in association with episodes of elevated sea temperatures over the past 20 years and involves the loss of the zooxanthellae following chronic photoinhibition. Mass bleaching has resulted in significant losses of live coral in many parts of the world. This paper considers the biochemical, physiological and ecological perspectives of coral bleaching. It also uses the outputs of four runs from three models of global climate change which simulate changes in sea temperature and hence how the frequency and intensity of bleaching events will change over the next 100 years. The results suggest that the thermal tolerances of reef-building corals are likely to be exceeded every year within the next few decades. Events as severe as the 1998 event, the worst on record, are likely to become commonplace within 20 years. Most information suggests that the capacity for acclimation by corals has already been exceeded, and that adaptation will be too slow to avert a decline in the quality of the world's reefs. The rapidity of the changes that are predicted indicates a major problem for tropical marine ecosystems and suggests that unrestrained warming cannot occur without the loss and degradation of coral reefs on a global scale.

The influence of supra-optimal root-zone temperatures on growth and stomatal conductance in Capsicum annuum L.

Pepper (Capsicum annuum L.) plants were grown aeroponically in a Singapore greenhouse under natural diurnally fluctuating ambient shoot temperatures, but at two different root-zone temperatures (RZTs): a constant 20 +/- 2 degrees C RZT and a diurnally fluctuating ambient (A) (25-40 degrees C) RZT, Plants grown at 20-RZT had more leaves, greater leaf area and dry weight than A-RZT plants. Reciprocal transfer experiments were conducted between RZTs to investigate the effect on plant growth, stomatal conductance (g(s)) and water relations. Transfer of plants from A-RZT to 20-RZT increased plant dry weight, leaf area, number of leaves, shoot water potential (Psi(shoot)), and g(s); while transfer of plants from 20-RZT to A-RZT decreased these parameters. Root hydraulic conductivity was measured in the latter transfer and decreased by 80% after 23 d at A-RZT. Transfer of plants from 20-RZT to A-RZT had no effect on xylem ABA concentration or xylem nitrate concentration, but reduced xylem sap pH by 0.2 units. At both RZTs, g(s) measured in the youngest fully expanded leaves increased with plant development. In plants with the same number of leaves, A-RZT plants had a higher g(s) than 20-RZT plants, but only under high atmospheric vapour pressure deficit. The roles of chemical signals and hydraulic factors in controlling g(s) of aeroponically grown Capsicum plants at different RZTs are discussed.

Cyclotron effective masses in layered metals

Many layered metals such as quasi-two-dimensional organic molecular crystals show properties consistent with a Fermi-liquid description at low temperatures. The effective masses extracted from the temperature dependence of the magnetic oscillations observed in these materials are in the range, m(c)*/m(e) similar to 1 - 7, suggesting that these systems are strongly correlated. However, the ratio m(c)*/m(e) contains both the renormalization due to the electron-electron interaction and the periodic potential of the lattice. We show that for any quasi-two-dimensional band structure, the cyclotron mass is proportional to the density-of-states at the Fermi energy. Due to Luttinger's theorem, this result is also valid in the presence of interactions. We then evaluate m(c) for several model band structures for the beta, kappa, and theta families of (BEDT-TTF)(2)X, where BEDT-TTF is bis-(ethylenedithia-tetrathiafulvalene) and X is an anion. We find that for kappa-(BEDT-TTF)(2)X, the cyclotron mass of the beta orbit, m(c)*(beta) is close to 2 m(c)*(alpha), where m(c)*(alpha) is the effective mass of the alpha orbit. This result is fairly insensitive to the band-structure details. For a wide range of materials we compare values of the cyclotron mass deduced from band-structure calculations to values deduced from measurements of magnetic oscillations and the specific-heat coefficient gamma.

Kinetics of propranolol uptake in muscle, skin, and fat of the isolated perfused rat hindlimb

The tissue distribution kinetics of a highly bound solute, propranolol, was investigated in a heterogeneous organ, the isolated perfused limb, using the impulse-response technique and destructive sampling. The propranolol concentration in muscle, skin, and fat as well as in outflow perfusate was measured up to 30 min after injection. The resulting data were analysed assuming (1) vascular, muscle, skin and fat compartments as well mixed (compartmental model) and (2) using a distributed-in-space model which accounts for the noninstantaneous intravascular mixing and tissue distribution processes but consists only of a vascular and extravascular phase (two-phase model). The compartmental model adequately described propranolol concentration-time data in the three tissue compartments and the outflow concentration-time curve (except of the early mixing phase). In contrast, the two-phase model better described the outflow concentration-time curve but is limited in accounting only for the distribution kinetics in the dominant tissue, the muscle. The two-phase model well described the time course of propranolol concentration in muscle tissue, with parameter estimates similar to those obtained with the compartmental model. The results suggest, first that the uptake kinetics of propranolol into skin and fat cannot be analysed on the basis of outflow data alone and, second that the assumption of well-mixed compartments is a valid approximation from a practical point of view las, e.g., in physiological based pharmacokinetic modelling). The steady-state distribution volumes of skin and fat were only 16 and 4%, respectively, of that of muscle tissue (16.7 ml), with higher partition coefficient in fat (6.36) than in skin (2.64) and muscle (2.79. (C) 2000 Elsevier Science B.V. All rights reserved.

Determination of T1pH relaxation rates in charred and uncharred wood and consequences for NMR quantitation

The performance of three different techniques for determining proton rotating frame relaxation rates (T1pH) in charred and uncharred woods is compared. The variable contact time (VCT) experiment is shown to over-estimate T1pH, particularly for the charred samples, due to the presence of slowly cross-polarizing C-13 nuclei. The variable spin (VSL) or delayed contact experiment is shown to overcome these problems; however, care is needed in the analysis to ensure rapidly relaxing components are not overlooked. T1pH is shown to be non-uniform for both charred and uncharred wood samples; a rapidly relaxing component (T1pH = 0.46-1.07 ms) and a slowly relaxing component (T1pH = 3.58-7.49) is detected in each sample. T1pH for each component generally decreases with heating temperature (degree of charring) and the proportion of rapidly relaxing component increases. Direct T1pH determination (via H-1 detection) shows that all samples contain an even faster relaxing component (0.09-0.24 ms) that is virtually undetectable by the indirect (VCT and VSL) techniques. A new method for correcting for T1pH signal losses in spin counting experiments is developed to deal with the rapidly relaxing component detected in the VSL experiment. Implementation of this correction increased the proportion of potential C-13 CPMAS NMR signal that can be accounted for by up to 50% for the charred samples. An even greater proportion of potential signal can be accounted for if the very rapidly relaxing component detected in the direct T1pH determination is included; however, it must be kept in mind that this experiment also detects H-1 pools which may not be involved in H-1-C-13 cross-polarization. (C) 2002 Elsevier Science (USA).

NMR characterization of blends of poly(hydroxybutyrate-co-hydroxyvalerate) with poly(vinyl acetate)

The extent of mixing in blends of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) (27% HV) and poly(vinyl acetate) (PVAc) has been measured using a number of different techniques, principally solid-state NMR. Differential scanning calorimetry DSC measurements indicated effective mixing of the polymer chains on a scale of several nanometres. The results of H-1 T-1 and H-1 T-1rho. measurements confirm intimate mixing of the chains. A change on blending in the H-1 T-1rho, and the H-1 NMR line width of the signal from the protons of PVAc was consistent with an increase in the amplitude and frequency of motion of this component. The PVAc chains reside within the inter-lamellar space, as confirmed by spin diffusion measurements after H-1 T-1rho preparation. (C) 2003 Society of Chemical Industry.

Expression, purification, crystallization, and NMR studies of the helicase interaction domain of Escherichia coli DnaG primase

in Escherichia coli, the DnaG primase is the RNA polymerase that synthesizes RNA primers at replication forks. It is composed of three domains, a small N-terminal zinc-binding domain, a larger central domain responsible for RNA synthesis, and a C-terminal domain comprising residues 434-581 [DnaG(434-581)] that interact with the hexameric DnaB helicase. Presumably because of this interaction, it had not been possible previously to express the C-terminal domain in a stably transformed E coli strain. This problem was overcome by expression of DnaG(434-581) under control of tandem bacteriophage gimel-promoters, and the protein was purified in yields of 4-6 mg/L of culture and studied by NMR. A TOCSY spectrum of a 2 mM solution of the protein at pH 7.0, indicated that its structured core comprises residues 444-579. This was consistent with sequence conservation among most-closely related primases. Linewidths in a NOESY spectrum of a 0.5 mM sample in 10 mM phosphate, pH 6.05, 0.1 M NaCl, recorded at 36 degreesC, indicated the protein to be monomeric. Crystals of selenomethionine-substituted DnaG(434-581) obtained by the hanging-drop vapor-diffusion method were body-centered tetragonal, space group I4(1)22, with unit cell parameters a = b 142.2 Angstrom, c = 192.1 Angstrom, and diffracted beyond 2.7 Angstrom resolution with synchrotron radiation. (C) 2003 Elsevier Inc. All rights reserved.