Reaction center light harvesting B875 complexes from Rhodocyclus gelatinosus: characterization and identification of quinones

Reaction center-B875 pigment-protein complexes were purified from Rhodocyclus gelatinosus. The proteic components consist of 7–8 polypeptides among which some were identified by their apparent molecular weights: the light harvesting B875 polypeptides and of 8 and 6 kDa, reaction center L (23 kDa), M (28 kDa) and H (34 kDa), cytochrome c (43 kDa). Four c-type hemes were found per reaction center. Flash-induced absorbance changes showed the presence of both Q_A and Q_B in the complex. Charge recombination times were determined to be: 1.16±0.2 (n=30) for P⁺Q_AQ_B ^- and 7–10 ms for P⁺Q_A ^- in presence of herbicides. From quinone analysis on one hand and kinetics of charge recombination on the other hand, we proposed that in the reaction center of Rhodocyclus gelatinosus Q_A is menaquinone 8 and Q_B is ubiquinone 8.     

Timemresolved fluorescence of S-100a protein: effect of Ca, Mg and unilamellar vesicles of egg phosphatidylcholine

Phase-modulation fluorescence lifetime measurements were used to study the single Trp residue of the Ca²⁺-binding protein S-100a both in the absence and in the presence of Ca²⁺ and/or Mg²⁺. Trp fluorescence decay for the protein was satisfactorily described by Lorentzian lifetime distributions centered around two components (approximately 4 ns and 0.5 ns). Lifetime values were unchanged by 2 mM Ca²⁺, but the fractional intensity associated with longer lifetime increased up to 75%. In the presence of Mg²⁺, the Ca²⁺ induced increase of the fractional intensity associated with longer lifetime was only 57%. For the protein in buffer, about the 85% of the recovered anisotropy was associated to a rotational correlation time of 6.7 ns. After the addition of Ca²⁺, this value was increased to 16.08 ns. In the presence of Mg²⁺, Ca⁺² increased the rotational correlation time to 33.75 ns. Similar studies were performed with S-100a interacting with egg phosphatidylcholine vesicles (SUV). Our data suggest that the conformation of the protein may be influenced by structural features of the lipidic membrane. Moreover, data obtained in the presence of Mg²⁺ indicate some interaction between lipids and S-100, likely mediated by this ion.     

Isolation and partial characterization of a new mutant for sterol biotransformation in Mycobacterium sp.

Summary A new sterol biotransforming mutant was isolated from NRRL-B3683 Mycobacterium sp. after nitrosoguanidine mutagenesis. The mutant showed an enhanced ability to biotransform stigmasterol into 17-ketosteroids compared with the parental strain.     

On the state of carotenoids bound to reaction centers of photosynthetic bacteria: A resonance raman study

The carotenoids bound to reaction centers of wild, Ga and GlC strains of Rhodopseudomonas spheroides, of Rhodospirillum rubrum, strain S1 and of Rhodopseudomonas viridis, yield very similar, but unusual resonance Raman spectra. Through a comparison with resonance Raman spectra of 15,15′-cis-β-carotene, these carotenoids are shown to assume cis conformations, while the corresponding chromatophores contain all-trans forms only. These cis conformations likely are identical for all the carotenoids studied. They remain unaffected by variations of temperature from 20 to 300 K as well as by the redox state of $\text{P-870}$. They are unstable, being rapidly isomerised towards the all-trans forms when extracted from the reaction centers. The possible nature of these conformers is discussed on the basis of their electronic and vibrational spectra.     

Micro‐ and nano‐scale mineralogical characterization of Fe(II)‐oxidizing bacterial stalks

Neutrophilic, microaerobic Fe(II)‐oxidizing bacteria (FeOB) from marine and freshwater environments are known to generate twisted ribbon‐like organo‐mineral stalks. These structures, which are extracellularly precipitated, are susceptible to chemical influences in the environment once synthesized. In this paper, we characterize the minerals associated with freshwater FeOB stalks in order to evaluate key organo‐mineral mechanisms involved in biomineral formation. Micro‐Raman spectroscopy and Field Emission Scanning Electron Microscopy revealed that FeOB isolated from drinking water wells in Sweden produced stalks with ferrihydrite, lepidocrocite and goethite as main mineral components. Based on our observations made by micro‐Raman Spectroscopy, field emission scanning electron microscopy and scanning transmission electron microscope combined with electron energy‐loss spectroscopy, we propose a model that describes the crystal‐growth mechanism, the Fe‐oxidation state, and the mineralogical state of the stalks, as well as the biogenic contribution to these features. Our study suggests that the main crystal‐growth mechanism in stalks includes nanoparticle aggregation and dissolution/re‐precipitation reactions, which are dominant near the organic exopolymeric material produced by the microorganism and in the peripheral region of the stalk, respectively.     

Using forest history and spatial patterns to identify potential high conservation value forests in Romania

Naturally dynamic forests have a high proportion of biotopes with old large trees, diverse vertical and horizontal structure at multiple scales, and much dead wood. As such, they provide habitat to species and ecosystem processes that forests managed for wood production cannot provide to the same degree. Whether termed old-growth, ancient, virgin, intact, primeval or continuity forests, a major challenge and need is to map such potential high conservation value forest for subsequent inclusion in functional habitat networks for biodiversity conservation in forest landscapes. Given that the delivery time of natural forest properties is much longer than of industry wood, we explore the usefulness of using historical maps to identify forests that have been continuously present for 220 years (potential old-growth) versus 140 years (potential aging forest) in a case study in the Romanian Carpathian Mountains (see Online Resource 1). While the total forest cover increased by 35 % over the past two centuries, the area of potential aging and potential old-growth forest declined by 56 and 34 %, respectively. Spatial modelling of edge effects and patch size for virtual species with different requirements indicated an even greater decrease in the area of functional habitat networks of old-growth and ageing forest. Our analyses show that compared to simple mapping of potential high conservation forests, the area of functional habitat patches is severely overestimated, and caution is needed when estimating the area of potential high conservation value forests that form functional habitat networks, i.e. a green infrastructure. In addition, the landscape and regional scale connectivity of patches needs to be considered. We argue that the use of historical maps combined with assessment of spatial patterns is an effective tool for identifying and analyzing potential high conservation value forests in a landscape context.     

Microplates as a microreactor platform for microalgae research

High‐throughput platforms for microalgae screening are not yet commercially available. In this study, the feasibility of 96‐well microplates was analyzed for microalgae research. Equivalence among wells, as culture microreactors, was investigated in controlled high CO₂ conditions. Specific growth rates of two microalgae species, Scenedesmus sp. UTEX1589 and an environmental isolate, were significantly higher in border wells than in internal positions. Furthermore, growth rate gradients analyzed as contours throughout the platform were observed for Scenedesmus sp. However, the output variable exhibited high precision associated with a low coefficient of variation (CV), between 6.8 and 7.8%. In a demonstrative experiment to determine the effect of culture media dilution on six microalgae species, treatments were randomized in the central subset of a microplate. Results were consistent and statistically sound (CV 9.4–12.9%), and showed that microalgae species could grow with no detrimental effect in 50% (v/v) dilution of the culture medium. Provided border wells exclusion and a randomized design, 96‐well microplates are a practical and statistical robust platform for microalgae research. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:638–644, 2013     

Novel materials based on DNA‐CTMA and lanthanide (Ce3+, Pr3+)

New, deoxyribonucleic acid (DNA) based compounds, functionalized with hexadecyltrimethylammonium chloride (CTMA) and lanthanide hydroxide nanoparticles were synthesized. The spectral measurements suggest that between the DNA‐CTMA complex and the lanthanide (III) ions a chemical interaction takes place. The obtained materials exhibit an improved fluorescence efficiency, showing a potential interest for application in photonics, and more particularly, in light emitting devices. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 613–617, 2016.