Alkaloids in Bulgarian Pancratium maritimum L

A GC/MS analysis of alkaloids from leaves, bulbs and roots of Pancratium maritimum was performed. From the identified 16 alkaloids, 5 alkaloids were reported for the first time for this plant. Several compounds with pharmacological activity were found. Haemanthamine was main alkaloid in the leaves and bulbs whereas galanthane was found to be main alkaloid in roots.     

Towards elucidating the energy of the first excited singlet state of xanthophyll cycle pigments by X-ray absorption spectroscopy

The first excited singlet state (S(1)) of carotenoids (also termed 2A(g)(-)) plays a key role in photosynthetic excitation energy transfer due to its close proximity to the S(1) (Q(y)) level of chlorophylls. The determination of carotenoid 2A(g)(-) energies by optical techniques is difficult; transitions from the ground state (S(0), 1A(g)(-)) to the 2A(g)(-) state are forbidden ("optically dark") due to parity (g <-- //--> g) as well as pseudo-parity selection rules (- <-- //--> -). Of particular interest are S(1) energies of the so-called xanthophyll-cycle pigments (violaxanthin, antheraxanthin and zeaxanthin) due to their involvement in photoprotection in plants. Previous determinations of S(1) energies of violaxanthin and zeaxanthin by different spectroscopic techniques vary considerably. Here we present an alternative approach towards elucidation of the optically dark states of xanthophylls by near-edge X-ray absorption fine structure spectroscopy (NEXAFS). The indication of at least one pi* energy level (about 0.5 eV below the lowest 1B(u)(+) vibronic sublevel) has been found for zeaxanthin. Present limitations and future improvements of NEXAFS to study optically dark states of carotenoids are discussed. NEXAFS combined with simultaneous optical pumping will further aid the investigation of these otherwise hardly accessible states.     

Pigment-protein architecture in the light-harvesting antenna complexes of purple bacteria: does the crystal structure reflect the native pigment-protein arrangement?

Structural analysis of crystallized peripheral (LH2) and core antenna complexes (LH1) of purple bacteria has revealed circular aggregates of high rotational symmetry (C₈, C₉ and C₁₆, respectively). Quantum-chemical calculations indicate that in particular the waterwheel-like arrangements of pigments should show characteristic structure-sensitive spectroscopic behavior in the near infrared absorption region. Laser-spectroscopic data obtained with non-crystallized, isolated LH2 of Rhodospirillum molischianum are in line with a highly symmetric (C₈) circular aggregate, but deviations have been found for LH2 of Rhodobacter sphaeroides and Rhodopseudomonas acidophila. For both the latter, C-shaped incomplete circular aggregates (as seen only recently in electron micrographs of crystallized LH1–reaction center complexes) may be a suitable preliminary model.     

Detection of the metastable rippled gel phase in hydrated phosphatidylcholine by fluorescence spectroscopy

Steady-state and time-resolved emission spectroscopy of 1-anilinonaphthalene-8-sulfonic acid (ANS) have been used for characterization of the metastable rippled gel phase, Pbeta'(mst), formed in fully-hydrated dipalmitoylphosphatidylcholine (DPPC) upon cooling from the liquid crystalline phase Lalpha [Tenchov et al., Biophys. J. 56 (1989) 757]. The Pbeta'(mst) phase of DPPC clearly differs from the stable Pbeta' phase by increased (approximately 27%) ANS emission intensity, by enhanced (approximately 23%) average radiative rate constant, and by reduced (approximately 18%) non-radiative quenching rate constant. The fluorescence intensity peak at the Pbeta'-->Lalpha transition temperature is replaced by a large, reversible stepwise intensity drop at the Pbeta'(mst)-->Lalpha transition. No such effects have been found for dimiristoylphosphatidylcholine (DMPC) dispersions confirming previous results that DMPC does not form a Pbeta'(mst) phase. Since ANS is known to predominantly reside in the interfacial region, the observed effects indicate differences between the stable and metastable rippled phases in the organization and dynamics of their lipid/water interfaces. The data demonstrate that the metastable rippled phase manifests its appearance also through interactions with small molecules (ANS size approximately 8 A).     

Two-photon excitation fluorescence spectrum of the light-harvesting complex LH2 from Chromatium minutissimum within 650-745 nm range is determined by two-photon absorption of bacteriochlorophyll rather than of carotenoids

Two-photon fluorescence excitation spectra of the peripheral light-harvesting complex LH2 from the purple photosynthetic bacterium Chromatium minutissimum were examined within the expected spectral range of the optically forbidden S1 singlet state of carotenoids. LH2 preparations isolated from wild-type and carotenoid-depleted cells were used. 100-fs laser pulses in the range of 1300-1490 nm with an energy of 7-9 mW (corresponding to one-photon absorption between 650 and 745 nm) were used for two-photon fluorescence excitation. It was shown that two-photon fluorescence excitation spectra of LH2 complex from wild and carotenoid-depleted cells are very similar to each other and to the two-photon fluorescence excitation spectrum of bacteriochlorophyll a in acetone. It was concluded that direct two-photon excitation of bacteriochlorophyll a determines the fluorescence of both samples within the 650-745 nm spectral range.     

Towards time-resolved, coupled structure-function information on carotenoid excited state processes: X-ray and optical short-pulse double resonance spectroscopy

A novel soft X-ray and optical short-pulse double resonance spectroscopic technique tailor-made to elucidate processes involving the optically forbidden S1 (2(1)A(g)) state of carotenoids in native biological samples (e.g., photosynthetic antenna complexes) is described. The principle relies on probing the near carbon K-edge absorption of the optically excited sample with soft X-rays generated by a laser-induced plasma. A first application concerns location of the 2(1)A(g) state of beta-carotene in vitro. Further applications are proposed.     

Reversion of nonsense mutants induced by 4-nitroquinoline-1-oxide in Schizosaccharomyces pombe.

We have studied the reversion of 8 nonsense alleles located in 7 different genes of Schizosaccharomyces pombe using 4-nitroquinoline-1-oxide (NQO) as a mutagenic agent. The nonsense mutants of S. pombe have been classified according to their suppressibility by defined opal and ochre suppressors into a class of efficiently suppressed opal and a class of inefficiency suppressed ochre mutants. The UGA alleles tested all revert consistently with NQO, in agreement with the high specificity of this mutagen for G-residues reported for bacteria and yeast. The UAA alleles show a lack or a low level of reversion with NQO. This low level of reversion is due to the low level of non-G-specific transversions at A sites of the UAA triplet. Within each class of nonsense mutants the extent of induction is site-dependent. We conclude that NQO acts predominantly on G-residues in S. pombe.     

Voluntary medical male circumcision: matching demand and supply with quality and efficiency in a high-volume campaign in Iringa Region, Tanzania

The government of Tanzania has adopted voluntary medical male circumcision (VMMC) as an important component of its national HIV prevention strategy and is scaling up VMMC in eight regions nationwide, with the goal of reaching 2.8 million uncircumcised men by 2015. In a 2010 campaign lasting six weeks, five health facilities in Tanzania's Iringa Region performed 10,352 VMMCs, which exceeded the campaign's target by 72%, with an adverse event (AE) rate of 1%. HIV testing was almost universal during the campaign. Through the adoption of approaches designed to improve clinical efficiency-including the use of the forceps-guided surgical method, the use of multiple beds in an assembly line by surgical teams, and task shifting and task sharing-the campaign matched the supply of VMMC services with demand. Community mobilization and bringing client preparation tasks (such as counseling, testing, and client scheduling) out of the facility and into the community helped to generate demand. This case study suggests that a campaign approach can be used to provide high-volume quality VMMC services without compromising client safety, and provides a model for matching supply and demand for VMMC services in other settings.