Chlorophyll a fluorescence: beyond the limits of the QA model

Chlorophyll a fluorescence is a non-invasive tool widely used in photosynthesis research. According to the dominant interpretation, based on the model proposed by Duysens and Sweers (1963, Special Issue of Plant and Cell Physiology, pp 353–372), the fluorescence changes reflect primarily changes in the redox state of Q_A, the primary quinone electron acceptor of photosystem II (PSII). While it is clearly successful in monitoring the photochemical activity of PSII, a number of important observations cannot be explained within the framework of this simple model. Alternative interpretations have been proposed but were not supported satisfactorily by experimental data. In this review we concentrate on the processes determining the fluorescence rise on a dark-to-light transition and critically analyze the experimental data and the existing models. Recent experiments have provided additional evidence for the involvement of a second process influencing the fluorescence rise once Q_A is reduced. These observations are best explained by a light-induced conformational change, the focal point of our review. We also want to emphasize that—based on the presently available experimental findings—conclusions on α/ß-centers, PSII connectivity, and the assignment of F_V/F_M to the maximum PSII quantum yield may require critical re-evaluations. At the same time, it has to be emphasized that for a deeper understanding of the underlying physical mechanism(s) systematic studies on light-induced changes in the structure and reaction kinetics of the PSII reaction center are required.     

A simple method for monitoring the cysteine content in synthetic peptides.

A new method for the determination of the cysteine content of synthetic peptides is described. For this purpose the classical amino acid analysis is not suitable, as cysteine may undergo oxidative dimerisation to cystine during the hydrolysis or evaporation. The intact peptide was reacted with N-ethylmaleimide (NEM) yielding a stable S-(N-ethylsuccinimido)-cysteine derivative, which could be separated by RP-HPLC and characterised by mass spectrometry. For the quantitative determination less than 0.1 microM peptide was sufficient.     

Intranasal Delivery of Human β-Amyloid Peptide in Rats: Effective Brain Targeting

(1) Intranasal administration is a non-invasive and effective way for the delivery of drugs to brain that circumvents the blood–brain barrier. The aims of the study were to test a nasal delivery system for human β-amyloid (Aβ) peptides, to measure the delivery of the peptides to brain regions, and to test their biological activity in rats. (2) Aβ_1-42, in the form of a mixture of oligomers, protofibrils, and fibrils was dissolved in a nasal formulation containing hydrophobic, hydrophylic, and mucoadhesive components. The peptide solution was administered intranasally to rats as a single dose or in repeated doses. (3) Nasally injected Aβ labeled with the blue fluorescent dye amino-methyl coumarinyl acetic acid (AMCA) could be detected by fluorescent microscopy in the olfactory bulb and frontal cortex. The concentration of the peptide was quantified by fluorescent spectroscopy, and a significant amount of AMCA-Aβ peptide could be detected in the olfactory bulb. Unlabeled Aβ also reached the olfactory bulb and frontal cortex of rats as evidenced by intense immunostaining. (4) In behavioral experiments, nasal Aβ treatment did not affect anxiety levels (open-field test) and short-term memory (Y-maze test), but significantly impaired long-term spatial memory in the Morris water maze. The treatments did not result in Aβ immunization. (5) The tested intranasal delivery system could successfully target a bioactive peptide into the central nervous system and provides a basis for developing a non-invasive and cost effective, new model to study amyloid-induced dysfunctions in the brain.     

Henneguya tunisiensis n. sp. (Myxosporea: Bivalvulida), a new gill parasite of Symphodus tinca (L.) (Teleostei: Labridae) off Tunisia

Henneguya tunisiensis n. sp., a new myxosporean, is described from the gill-arches of the East Atlantic peacock wrasse Symphodus tinca (L.) collected from off the Kerkennah Islands, Tunisia. It is characterised by the presence of elongate white plasmodia of 1–1.5 × 1.5–2 mm in size. The mature spores are rounded in frontal view and have two identical polar capsules and two caudal appendages which taper considerably at the end. Both light and electron microscopical data show that this species differs in several morphological features from all previously described Henneguya spp. A molecular analysis, based on 18S rDNA sequence data, indicates that H. tunisiensis n. sp. is readily distinguishable from other myxozoan DNA sequences in GenBank. Phylogenetically, the new species is placed in the marine Henneguya clade, which is a sister group of marine Myxobolus spp. from perciform fishes in Tunisian waters.     

Neuroprotective effect of small heat shock protein,Hsp27, after acute and chronic alcohol administration

Alcohol induces degeneration of neurons and inhibits neurogenesis in the brain. Small heat shock proteins are able to protect neurons in cerebral ischemia and oxidative stress. In this study, we investigated the neuroprotective effect of small heat shock protein, Hsp27, after acute and chronic ethanol administrations using transgenic mice overexpressing the human Hsp27 protein. Transgenic mice and wild-type littermates were injected with 2 g/kg ethanol intraperitoneally, and then motor coordination and muscle strength were analyzed using different behavioral tests, such as footprint analysis, balance beam, and inverted screen tests. Ethanol-injected transgenic mice showed similar footprints to control saline-injected mice, did not fall of the beam, and were able to climb to the top of the inverted screen, while wild-type mice showed ataxia and incoordination after ethanol injection. The effect of Hsp27 on chronic ethanol consumption was also investigated. Drinking water of mice was replaced by a 20% ethanol solution for 5 weeks, and then brain sections were stained with Fluoro Jade C staining. We found significantly lesser amount of degenerating neurons in the brain of ethanol-drinking transgenic mice compared to wild-type mice. We conclude that Hsp27 can protect neurons against the acute and chronic toxic effects of ethanol.     

Synthesis and biological evolution of hydrazones derived from 4-(trifluoromethyl)benzohydrazide

Reflecting the known biological activity of isoniazid-based hydrazones, seventeen hydrazones of 4-(trifluoromethyl)benzohydrazide as their bioisosters were synthesized from various benzaldehydes and aliphatic ketones. The compounds were screened for their in vitro activity against Mycobacterium tuberculosis, nontuberculous mycobacteria (M. avium, M. kansasii), bacterial and fungal strains. The most antimicrobial potent derivatives were also investigated for their cytostatic and cytotoxic properties against three cell lines. Camphor-based molecule, 4-(trifluoromethyl)-N′-(1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)benzohydrazide, exhibited the highest and selective inhibition of M. tuberculosis with the minimum inhibitory concentration (MIC) of 4?µM, while N′-(4-chlorobenzylidene)-4-(trifluoromethyl)benzohydrazide was found to be superior against M. kansasii (MIC?=?16?µM). N′-(5-Chloro-2-hydroxybenzylidene)-4-(trifluoromethyl)benzohydrazide showed the lowest MIC values for gram-positive bacteria including methicillin-resistant Staphylococcus aureus as well as against two fungal strains of Candida glabrata and Trichophyton mentagrophytes within the range of ≤0.49–3.9?µM. The convenient substitution of benzylidene moiety at the position 4 or the presence of 5-chloro-2-hydroxybenzylidene scaffold concomitantly with a sufficient lipophilicity are essential for the noticeable antimicrobial activity. This 5-chlorosalicylidene derivative avoided any cytotoxicity on two mammalian cell cultures (HepG2, BMMΦ) up to the concentration of 100?µM, but it affected the growth of MonoMac6 cells.     

Conserved structure of the chloroplast-DNA encoded D1 protein is essential for effective photoprotection via non-photochemical thermal dissipation in higher plants

Naturally selected atrazine-resistant (AR) weeds possessing a Ser₂₆₄ → Gly D1 protein encoded by a mutant psbA allele in the chloroplast-DNA have increased photosensitivity and lower fitness. The D1 mutant lines of S. nigrum revealed impaired regulation of photosystem II (PSII) activity as compared with the wild-type plants resulting in a less effective photochemical light utilization and in addition, a lower capacity of non-photochemical thermal dissipation (NPQ), one of the main photoprotective mechanisms in oxygenic photosynthetic organisms. In this work, comparative chlorophyll fluorescence analysis in attached leaves of wild-type and AR Solanum nigrum L. and in their reciprocal crosses has been used to establish how the lower NPQ is inherited. Both a 50% reduction in steady-state NPQ and a 60–70% reduction in the rapidly reversible, energy-dependent (qE) component of NPQ were common phenomena in the parent and hybrid lines of D1 mutant S. nigrum. The nuclear hybrid status of the F2 plant material was confirmed by morphological observations on fully developed leaves. No alteration was found in the nucleotide sequence and the deduced amino acid sequences of the nuclear psbS gene isolated from different biotypes of S. nigrum, and there were no differences in the expressions of both the PsbS and the D1 proteins. All things considered, co-inheritance of the lower photoprotective NPQ capacity and the Ser₂₆₄ → Gly D1 protein mutation was clearly observed, suggesting that the evolutionarily conserved D1 structure must be indispensable for the efficient NPQ process in higher plants.     

Peptide based vaccine design: synthesis and immunological characterization of branched polypeptide conjugates comprising the 276-284 immunodominant epitope of HSV-1 glycoprotein D.

The importance of the length and conjugation site of a protective epitope peptide (276SALLEDPVG284) from glycoprotein D of herpes simplex virus in branched polypeptide conjugates has been investigated. A new set of peptides, with a single attachment site and truncated sequences, was prepared. The immunogenicity of conjugates and the specificity of antibody responses elicited were investigated in BALB/c, C57/B1/6 and CBA mice. It was found that the covalent coupling of the peptide comprising the 276-284 sequence of gD through its Asp residue at position 281 did not influence the immunogenic properties of the epitope, while involvement of the side chain of Glu at position 280 almost completely abolished immunogenicity. These results clearly indicated that the conjugation site of the epitope peptide influenced the intensity and specificity of antibody responses. Comparison of the immunological properties of conjugates containing truncated gD peptides revealed the presence of two epitopes within the 276-284 region. One of the proposed epitopes is situated at the N-terminal (276-281) region, while the other is located at the C-terminal end of the sequence (279-284). Binding data demonstrated that some of the peptides comprising these epitopes induced gD-specific responses in their conjugated form and also elicited an immune response that conferred protection against lethal HSV-1 infection. The correlation of peptide- and gD-specific antibody responses with the protective effect of the immune response is discussed.