Book review

H. D. Holland, The Chemical Evolution of the Atmosphere and Oceans. Princeton University Press, Princeton, N.J., 1984. 94 tables and 230 figures, xii + 582 pp., $75.00; paper $24.00.     

Synthesis and characterization of four novel mixed (porphyrinato)(phthalocyaninato) sandwich-type europium(III) complexes with [tetrakis(4-chlorophenyl)porphyrinato] and diversely substituted phthalocyaninato ligands

Four novel mixed (porphyrinato)(phthalocyaninato) rare earth double-deckers Eu^III(TClPP)[Pc(t-BuPhO₂)₄] {H₂TClPP = tetrakis(4-chlorophenyl)porphyrin, H₂[Pc(t-BuPhO₂)₄] = 1,3,10,12(11,13),19,21(20,22),28,30(29,31)-octa-tert-butyl-tetrakis[1,4]benzodioxino[2,3-b:2′,3′-k:2″,3″-t:2?,3?-e₁]phthalocyanine}, HEu^III(TClPP)[Pc(α-OC₄H₉)₈] {H₂[Pc(α-OC₄H₉)₈] = 1,4,8,11,15,18,22,25-octa-butoxy-phthalocyanine}, Eu^III(TClPP)[Pc(MeOPhO)₈]{H₂[Pc(MeOPhO)₈] = 2,3,9,10,16,17,23,24-octakis(4-methoxyphenoxy)phthalocyanine} and Eu^III(TClPP)[Pc(PhS)₈] {H₂[Pc(PhS)₈] = 2,3,9,10,16,17,23,24-octakis(benzenesulfenyl)phthalocyanine} have been prepared for the first time by treating Eu(acac)(TClPP) with corresponding metal-free phthalocyanine in refluxing 1,2,4-trichlorobenzene (TCB). Typical IR marker bands of the monoanion radical , and show strong bands at 1310, 1319, and 1318 cm⁻¹, and are attributed to pyrrole CC stretchings. The TClPP⁻ IR marker band at ca. 1270-1300 cm⁻¹ was not observed for these compounds. These facts indicate that the hole in these double-deckers is mainly localized at the phthalocyanine ring. The marker IR band for phthalocyanine monoanionradical, , appearing at ca. 1312 cm⁻¹ as a medium absorption band was not observed for HEu^III(TClPP)[Pc(α-C₄H₉)₈]. Instead, a significant peak appearing at ca. 1321 cm⁻¹ with weak intensity is assigned to the pyrrole stretching of the phthalocyanine dianion, . This suggests that both the phthalocyanine and porphyrin rings exist as dianions in mixed (porphyrinato)(phthalocyaninato) complex, . The four complexes were characterized by MS, EA, UV-Vis and IR spectra.     

Reduction of hyperhydricity in the culture of <Emphasis Type="Italic">Lepidium meyenii</Emphasis> shoots by the addition of rare earth elements

Adventitious shoots induced from maca calli on induction media without rare earth elements (REE) had higher water content and lower soluble protein concentration when compared with shoots sprouted from maca seeds. Due to lower activities of antioxidative enzymes, there were higher concentrations of H₂O₂ and malonyldialdehyde (MDA) in adventitious shoots than those in seed shoots. When La³⁺, Ce³⁺ and Nd³⁺ (0.04 mM to 0.1 mM) were added to induction media, induction rates of the adventitious shoots were only affected slightly, but hyperhydricity rates were significantly reduced. La³⁺, Ce³⁺ or Nd³⁺ enhanced the activities of antioxidative enzymes in adventitious shoots, e.g. peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR). When the concentrations of La³⁺, Ce³⁺ and Nd³⁺ were 0.1 mM, the oxygen stress in adventitious shoots was decreased to levels similar to seed shoots, where most adventitious shoots grew normally.     

Cloning,sequencing, overexpression and characterization of <Emphasis Type="SmallCaps">l</Emphasis>-rhamnose isomerase from <Emphasis Type="Italic">Bacillus pallidus</Emphasis> Y25 for rare sugar production

The l-rhamnose isomerase gene (L -rhi) encoding for l-rhamnose isomerase (l-RhI) from Bacillus pallidus Y25, a facultative thermophilic bacterium, was cloned and overexpressed in Escherichia coli with a cooperation of the 6×His sequence at a C-terminal of the protein. The open reading frame of L -rhi consisted of 1,236 nucleotides encoding 412 amino acid residues with a calculated molecular mass of 47,636 Da, showing a good agreement with the native enzyme. Mass-produced l-RhI was achieved in a large quantity (470 mg/l broth) as a soluble protein. The recombinant enzyme was purified to homogeneity by a single step purification using a Ni-NTA affinity column chromatography. The purified recombinant l-RhI exhibited maximum activity at 65°C (pH 7.0) under assay conditions, while 90% of the initial enzyme activity could be retained after incubation at 60°C for 60 min. The apparent affinity (K _m) and catalytic efficiency (k _cat/K _m) for l-rhamnose (at 65°C) were 4.89 mM and 8.36 × 10⁵ M⁻¹ min⁻¹, respectively. The enzyme demonstrated relatively low levels of amino acid sequence similarity (42 and 12%), higher thermostability, and different substrate specificity to those of E. coli and Pseudomonas stutzeri, respectively. The enzyme has a good catalyzing activity at 50°C, for d-allose, l-mannose, d-ribulose, and l-talose from d-psicose, l-fructose, d-ribose and l-tagatose with a conversion yield of 35, 25, 16 and 10%, respectively, without a contamination of by-products. These findings indicated that the recombinant l-RhI from B. pallidus is appropriate for use as a new source of rare sugar producing enzyme on a mass scale production.     

Dispersal-limited species – A challenge for ecological restoration

In recent years, increasing efforts have been directed to the restoration of natural communities affected by human activities. However, restoration success is often reduced because of the lack of dispersal-limited species in the restored site. Numerous rare species are dispersal-limited, having low probabilities to re-colonize restored sites and to establish viable populations. A high species richness enhances the ability of ecosystems to maintain multiple functions. It has been shown that in highly diverse ecosystems such as alpine meadows, tropical forests and coral reefs, the most distinct combinations of functions are supported predominantly by rare species. Thus, more emphasis should be given to support rare species in restoration actions. I suggest that well-known techniques for increasing plant diversity in restoration projects should be complemented with techniques to re-introduce dispersal-limited animals. Re-establishing ecological connectivity might be of benefit for certain species in the long term. However, for the majority of dispersal-limited animal species, translocations of founder individuals might be the only tool to re-establish populations in restored sites.     

Optical properties of CaAl(SO4)2Br:RE (RE = Dy,Eu, Ce) novel phosphors

A new phosphor CaAl(SO₄)₂Br doped with Dy, Ce and Eu is reported. Rare earth (Dy, Eu and Ce)‐doped polycrystalline CaAl(SO₄)₂Br phosphors were prepared using a wet chemical reaction method and studied for X‐ray diffraction and photoluminescence (PL) characteristics. Dy³⁺ emission in the CaAl(SO₄)₂Br lattice was observed at 484 and 574 nm in the blue and yellow regions of the spectrum, which are assigned to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions of the Dy³⁺ ion, respectively. While the PL emission spectra of CaAl(SO₄)₂Br:Ce phosphor showed Ce³⁺ emission at 347 nm due to 5d → 4f transition of the Ce³⁺ ion. In a CaAl(SO₄)₂Br:Eu lattice, Eu³⁺ emissions were observed at 593 and 617 nm, coming from the ⁵D₀ → ⁷ F₁ and ⁵D₀ → ⁷ F₂ electron transitions, respectively. The PL study showed that the intensity of electric dipole transition at 617 nm dominates over that of magnetic dipole transition at 590 nm. The maximum PL intensity was obtained for a 1 mol% concentration of Eu³⁺ in CaAl(SO₄)₂Br host lattice. The results showed that the material may be a promising candidate as a blue‐, yellow‐ and red‐emitting phosphor. Copyright © 2013 John Wiley & Sons, Ltd.     

Effects of inbreeding and pollen donor provenance and diversity on offspring performance under environmental stress in the rare plant Cochlearia bavarica

Habitat degradation and loss can reduce size and genetic variability of natural populations, increasing individual homozygosity and average relatedness between individuals. While the resulting inbreeding depression may be reduced by natural selection under prevailing environmental conditions, it may increase again under environmental stress. To investigate the effect of environmental stress on offspring performance and the expression of inbreeding depression, we hand-pollinated maternal plants in small (< 100, n=5) and large populations (> 400 flowering plants, n=5) of the rare plant Cochlearia bavarica (Brassicaceae) and raised the offspring under experimentally manipulated water and light regimes (normal or reduced supply). In addition to considering natural variation in inbreeding levels due to population size, we manipulated pollen donor provenance and diversity. Maternal plants were pollinated with nine donors from a different population or with one or nine donors from the same population. One further inflorescence of each maternal plant was exposed to free pollination. Offspring growth and survival were monitored over 300 days. Offspring performance varied significantly among populations and maternal plants. Environmental stress interacted significantly with these factors. However, there was no general indication that offspring from small populations were more negatively affected. In seven out of 10 populations, offspring derived from between-population pollination performed better than offspring derived from within-population pollination. Also, in five out of 10 populations, average offspring size was higher after within-population pollination with nine than after pollination with one pollen donor. These results suggest low genetic diversity within C. bavarica populations, both smaller and larger ones. Interactions between environmental stress and pollination treatment indicated that using pollen donors from outside a population or increasing the number of pollen donors can reduce inbreeding depression, but that this beneficial effect is impaired under stressful conditions.     

Cloning and characterization of a novel <Emphasis Type="SmallCaps">l</Emphasis>-arabinose isomerase from <Emphasis Type="Italic">Bacillus licheniformis</Emphasis>

Based on analysis of the genome sequence of Bacillus licheniformis ATCC 14580, an isomerase-encoding gene (araA) was proposed as an l-arabinose isomerase (L-AI). The identified araA gene was cloned from B. licheniformis and overexpressed in Escherichia coli. DNA sequence analysis revealed an open reading frame of 1,422 bp, capable of encoding a polypeptide of 474 amino acid residues with a calculated isoelectric point of pH 4.8 and a molecular mass of 53,500 Da. The gene was overexpressed in E. coli, and the protein was purified as an active soluble form using Ni–NTA chromatography. The molecular mass of the purified enzyme was estimated to be ~53 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and 113 kDa by gel filtration chromatography, suggesting that the enzyme is a homodimer. The enzyme required a divalent metal ion, either Mn²⁺or Co²⁺, for enzymatic activity. The enzyme had an optimal pH and temperature of 7.5 and 50°C, respectively, with a k _cat of 12,455 min⁻¹ and a k _cat/K _m of 34 min⁻¹ mM⁻¹ for l-arabinose, respectively. Although L-AIs have been characterized from several other sources, B. licheniformis L-AI is distinguished from other L-AIs by its wide pH range, high substrate specificity, and catalytic efficiency for l-arabinose, making B. licheniformis L-AI the ideal choice for industrial applications, including enzymatic synthesis of l-ribulose. This work describes one of the most catalytically efficient L-AIs characterized thus far.     

l-Xylose and l-lyxose production from xylitol using Alcaligenes 701B strain and immobilized l-rhamnose isomerase enzyme

Xylitol was used as a raw material for production of l-xylose and l-lyxose using Alcaligenes 701B strain and immobilized l-rhamnose isomerase enzyme. Alcaligenes 701B converted xylitol to l-xylulose with a yield of 34% in the bioreactor. l-Xylulose was converted to l-xylose and l-lyxose using immobilized l-rhamnose isomerase enzyme. The final equilibrium between l-xylulose, l-xylose and l-lyxose was 53:26:21. The enzyme assays indicated that Alcaligenes 701B strain has an NAD-dependent xylitol dehydrogenase enzyme responsible for l-xylulose production. Furthermore, NAD(P)H-dependent l-xylulose reductase enzyme was active during conversion of xylitol to l-xylulose. The highest l-xylulose production rate corresponded with the highest growth rate. The Alcaligenes 701B strain used d-xylose for biomass growth, but xylitol was used only for l-xylulose production during conversion phase.     

Using phylogenetic, genetic and demographic evidence for setting conservation priorities for Mexican rare pines

Phylogenetic, genetic and demographic information are key issues for establishing priorities for conservation. In this study we explored the Vane-Wrigth measure of phylogenetic diversity for establishing criteria for conservation, when intra as well as interpopulation level demographic (population size) and genetic (heterozygosity, inbreeding and genetic distances among populations) parameters are taken into consideration. The data were standardized and analyzed independently and integratively enabling the calculation of indices or criteria for conservation priorities. We illustrate the application of this approach in populations of four Mexican pine species that have been considered rare and endangered, Pinus rzedowzkii, P. pinceana, P. lagunae and P. muricata. The application of several independent diversity indices did not allow us to resolve prioritization. However, the integration of all indices generated different values of importance to conservation, and suggested that the populations with the highest priorities for conservation are: two for Pinus rzedowskii, P. pinceana, and P. lagunae, and one for P. muricata. These populations have intermediate sizes, are the most divergent in the phylogeny and contain genetic variation that is representative of the gene pool of each species. Finally, we demonstrated the functionality of some genetic and demographic parameters; the genetic structure, recruitment rate, geographic distribution and demographic stochasticity, as complementary indicators for evaluating the conservation priority among populations and species.