The peridinin chlorophyll-a protein (PCP) of dinoflagellates differs from the well-studied light-harvesting complexes of purple bacteria and green plants in its large (4:1) carotenoid to chlorophyll ratio and the unusual properties of its primary pigment, the carotenoid peridinin. We utilized ultrafast polarized transient absorption spectroscopy to examine the flow of energy in PCP after initial excitation into the strongly allowed peridinin S2 state. Global and target analysis of the isotropic and anisotropic decays reveals that significant excitation (25-50%) is transferred to chlorophyll-a directly from the peridinin S2 state. Because of overlapping positive and negative features, this pathway was unseen in earlier single-wavelength experiments. In addition, the anisotropy remains constant and high in the peridinin population, indicating that energy transfer from peridinin to peridinin represents a minor or negligible pathway. The carotenoids are also coupled directly to chlorophyll-a via a low-lying singlet state S1 or the recently identified SCT. We model this energy transfer time scale as 2.3 +/- 0.2 ps, driven by a coupling of approximately 47 cm(-1). This coupling strength allows us to estimate that the peridinin S1/SCT donor state transition moment is approximately 3 D.

We present laser flash-induced triplet-minus-singlet (TmS(flash)) and absorbance-detected-magnetic-resonance (TmS(ADMR)) measurements on the light-harvesting chlorophyll a/b pigment-protein complex (LHCII) from pea. We investigated the influence of LHCII aggregation on xanthophyll triplet formation. The effect of aggregation was previously studied using TmS(ADMR) [van der Vos et al. (1994) Biochim. Biophys. Acta 1208, 243-250] for LHCII from spinach, and it was concluded that aggregation leads to a large increase of the amount of intertrimer triplet transfer. However, a similar study on LHCII from pea with the use of TmS(flash) measurements [Barzda et al. (1998) Biochemistry 37, 546-561] showed much smaller effects. To resolve this apparent discrepancy and to compare the results of TmS(ADMR) and TmS(flash) measurements, we used both techniques to study LHCII from pea, applying an identical aggregation procedure in both cases. It appears that aggregation does not lead to an increase of intertrimer triplet transfer as thought before but to a redistribution of the triplets over the two central xanthophylls (mainly lutein) that are present in each monomeric subunit of LHCII. Moreover, it is argued that the TmS band at 525 nm is due to lutein instead of violaxanthin as was reported in earlier studies. It is concluded that aggregation leads to a change in chlorophyll-xanthophyll interactions, which might explain the large change in excited-state lifetime of chlorophyll a in LHCII upon aggregation. This change in lifetime is possibly related to the phenomenon of nonphotochemical quenching in green plants, which is an important protective regulatory mechanism, that lowers the probability of photoinhibition.

The Optical Dynamics of Excitons in Cylindrical J-Aggregates Lampoura, S.S.; Spitz, C.; Dähne, S.; Knoester, Jasper; Duppen, K.; Dahne, S. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Research and Testing, Richard-Willstaetter-Strasse 11, D-12489 Berlin, Germany. ReceiVed: September 12, 2001; In Final Form: NoVember 28, 2001 The optical dynamics of excitons in cylindrical 5,5′,6,6′-tetrachloro-1,1′-diethyl-3,3′-di(4-sulfobutyl)-benzimidazolocarbocyanine (TDBC)/C8O3 aggregates have been investigated by ultrafast pump-probe spectroscopy and accumulated photon echo experiments. In the nonlinear optical interactions, both the oneexciton band and the two-exciton band are excited. The interpretation of the results involves the separation of the two-exciton states into two types: those that have predominantly "ring"-character, with energy separations determined by the circumference of the cylinder, and those that have predominantly "longitudinal"-character, with energy separations determined by the coherence length of the excitons along the length of the cylinder. At 1.5 K, the excitons were found to be delocalized over an area of, on average, 95 molecules. These excitons can move incoherently to other localized regions on the cylinder, leading to rapid relaxation within the oneexciton band.

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Exciton dynamics in the B850 and B875 bands of isolated complexes of Rhodopseudomonas acidophila (strain 10 050 and 7050) and in the B875 band of isolated complexes of Rhodobium marinum were investigated by means of accumulated photon echo and pump-probe techniques at different temperatures and wavelengths. For all three systems, the optical dephasing time T 2 was found to be very similar: at 4.2 K, T 2 is 116 and 106 ps for the B850 and B875 bands of Rhodopseudomonas acidophila, respectively, and 93 ps for the B875 band of Rhodobium marinum. The rapid dephasing, which displays glassy character, is a consequence of the strong pigment-protein interactions that arise through the rather short distances in these complexes. The observed dephasing time at the red edge of the B850 band of Rhodopseudomonas acidophila at 4.2 K reveals the existence of spectral diffusion in this system. From the wavelength dependence of the pump-probe signal in the B875 LH1 band of Rhodopseudomonas acidophila at 3 K it is concluded that energy transfer between energetically inequivalent LH1 rings occurs on a time scale of several tens picoseconds, while energy trapping takes place in about 250 ps.

BackgroundThe aortic Dacron wrapping technique is a surgical technique used under certain circumstances in cases of ascending aorta dilatation. Herein, we are presenting our experience on the method performed on multimorbid patients who denied major aortic surgery.MethodsWe included in our series 7 patients (5 male-2 female) with mild to moderate ascending aortic dilatation, who were operated with the wrapping technique. One patient was submitted to biological aortic valve replacement during the same procedure. The number of conventionally operated patients during the same period (2 years) was 21.ResultsMortality during the 18-months follow-up control was 0%. One patient had to be operated with biological aortic valve replacement 18 months after the initial wrapping operation, although the diameter of her ascending aorta remained stable.ConclusionsThe Dacron wrapping technique is a method that can alternatively be used in multimorbid patients with mild to moderate ascending aortic dilatation without dissecting elements and has generally good results.

Glaucoma, the most common form of which is primary open-angle glaucoma (POAG), is a neurodegenerative disease which is the second most common cause of blindness worldwide. Among the factors that have been implicated in the pathophysiology of this disease is infection with Helicobacter pylori. This alleged association has caused a great deal of scientific discussion during the past decade, as the establishment of such a correlation might lead to therapeutic applications for all glaucoma patients. In this review, we assess all relevant major studies and trials in an effort to elucidate the issue.

AimTo investigate the reasons that lead to postponement of cardiac operations, in order to elucidate the problem and help patients through modes of prevention.Methods-DesignWe retrospectively included in the study all patients submitted to elective adult heart surgery in our department during the 4-year period 2007-2010 and noted all cases of postponement after official inclusion in the operating schedule.Results94 out of a total of 575 patients (16.34%) scheduled for elective cardiac operation had their procedure postponed. The reasons were mainly organisatory (in 49 cases, 52.12%), which in order of significance were: unavailability in operating rooms, shortage in matching erythrocyte units and shortage in anaesthetic/nursing staff. The rest of the cases (45, 47.88%) were postponed due to medical reasons, which in order of significance were: febrile situations, including infections of the respiratory, gastrointestinal and urinary system, problems with the regulation of antiplatelet and antithrombotic drugs, neurological manifestations such as stroke and transient ischaemic attacks, exacerbation of asthma/chronic obstructive pulmonary disease, arrhythmias, renal problems and allergic reactions to drugs. Patients with advanced age and increased Euroscore values were most possible to have their heart operation postponed.ConclusionsHeart operations are postponed due to organisatory as well as medical reasons, the latter mainly affecting older, morbid patients who therefore require advanced preoperative care.