Hydrogen sulphide infiltration downregulates oxidative metabolism and extends postharvest life of banana

Hydrogen sulphide (H₂ S) has emerged as a potential regulator of plant defence against different abiotic stresses. As a climacteric fruit, banana undergoes oxidative stresses shortly after harvest, resulting in faster ripening and senescence. This work examines the effects of vacuum infiltrated H₂ S on ripening inhibition of banana. Banana fruits were vacuum infiltrated with 1 mm H₂ S. Effects on oxidative stress markers, physiological changes, bioactive compounds and antioxidant potentials were examined during storage at 25 °C and 75-80% RH. Results indicate that treated fruits were less affected by oxidative stress, as evident by lower accumulation of ROS (superoxide and peroxide ions), elevated phenols content and antioxidant capacity. The ripening inhibitory effects of H₂ S delayed chlorophyll loss and reduced ethylene and CO₂ production. H₂ S infiltration also reduced MDA accumulation and electrolytic leakage, resulting in longer shelf life. Vacuum infiltration with H₂ S had a protective effect on postharvest banana through overcoming the deleterious effect of ROS and strengthening antioxidant potential. Thus, this method could be promising for enhanced preservation of banana during storage.

Effect of postharvest hydrogen sulphide on lignification and biochemical markers of pointed gourd

Hydrogen sulphide (H₂ S) has emerged as a gasotransmitter molecule that modulates several physiological functions in plants, specially, different biotic and abiotic stresses. Pointed gourd (PG) fruits start losing their soft texture and appealing colour within 2-3 days of harvest, resulting in poor marketability and shelf life. Here, the effect of exogenous H₂ S (1 and 2 mm) application on lignification and other biochemical markers linked to ripening, shelf-life and edible quality of PG was assessed during cold (12 °C, 85-90% RH) and ambient (27 ± 2 °C, 55 ± 5% RH) storage. The synergistic effect of H₂ S was recorded during simulated storage at ambient conditions. Postharvest H₂ S treatment (1 mm) effectively delayed yellowing and chlorophyll loss (four-fold reduction) and maintained the phenolic content and higher antioxidant activity (36%). The H₂ S-treated PG fruits had significantly lower lignification and membrane permeability i.e. 15% and 13%, respectively, than control samples. H₂ S-treated fruit also maintained higher PAL and lower PPO activity. Therefore, postharvest application of H₂ S (2 mm) could be effective in maintaining postharvest quality of PG fruits and extending the marketing period.

New antiherpetic 1,3-phenylene derivatives, inhibitors of the interaction of the HSV-1 origin binding protein (OBP) with DNA

The synthesis of new 1,3-phenylene derivatives and their preliminary evaluation as antivirals (Herpes simplex 1, HSV-1) whose antiherpetic activity can be related with the inhibition of the interaction of the origin binding protein (OBP) with the DNA are presented. The new compounds are adjusted to a previously defined common structural model, consisting of a central aromatic system, which presents two side chains of different lengths in relative position 1, 3; these chains are made up of atomic groups characterized by the alternation of positive and negative centers, situating differently substituted rings, preferably aromatic, at the ends of both chains. Some of these derivatives, such as N,N''-(4-methoxy-1,3-phenylene)bis[N'-(4-nitrophenyl)urea] (2c) or (1,3-phenylene)bis[N-(p-tolyl)aminosulfonyl] (11b), show antiherpetic activity related to the proposed mechanism.

Functional analysis of human cytomegalovirus polymerase accessory protein

The human cytomegalovirus (HCMV) UL44 gene product, polymerase accessory protein, was cloned and expressed in Escherichia coli as a 53,000 MW protein. The activity of HCMV DNA polymerase (Pol) alone and Pol/UL44 complex was evaluated in Pol assays designed specifically to elucidate Pol/UL44 interactions. Addition of UL44 to HCMV Pol with primed, single-stranded DNA resulted in increased incorporation of nucleotides into DNA, which was correlated with enhanced enzyme processivity. Several deletion mutants which span the UL44 sequence were constructed and examined for the ability to stimulate Pol activity and to bind double-stranded DNA. The functional domains of UL44 protein were determined to reside within the N-terminal 309 amino acids of the wild type sequence, since deletions within this region resulted in loss of DNA binding and the ability to stimulate Pol. Deletion of C-terminal amino acids 310-433 had no effect on the ability of UL44 protein to increase the processivity of HCMV DNA Pol.

Characterization of the antigenic structure of herpes simplex virus type 1 glycoprotein C through DNA sequence analysis of monoclonal antibody-resistant mutants

Earlier studies of a group of monoclonal antibody-resistant (mar) mutants of herpes simplex virus type 1 glycoprotein C (gC) operationally defined two distinct antigenic sites on this molecule, each consisting of numerous overlapping epitopes. In this report, we further define epitopes of gC by sequence analysis of the mar mutant gC genes. In 18 mar mutants studied, the mar phenotype was associated with a single nucleotide substitution and a single predicted amino acid change. The mutations were localized to two regions within the coding sequence of the external domain of gC and correlated with the two previously defined antigenic sites. The predicted amino acid substitutions of site I mutants resided between residues Gln-307 and Pro-373, whereas those of site II mutants occurred between amino acids Arg-129 and Glu-247. Of the 12 site II mutations, 9 induced amino acid substitutions within an arginine-rich segment of 8 amino acids extending from residues 143 to 151. The clustering of the majority of substituted residues suggests that they contribute to the structure of the affected sites. Moreover, the patterns of substitutions which affected recognition by antibodies with similar epitope specificities provided evidence that epitope structures are physically linked and overlap within antigenic sites. Of the nine epitopes defined on the basis of mutations, three were located within site I and six were located within site II. Substituted residues affecting the site I epitopes did not overlap substituted residues of site II, supporting our earlier conclusion that sites I and II reside in spatially distinct antigenic domains. A computer analysis of the distribution of charged residues and the predicted secondary structural features of wild-type gC revealed that the two antigenic sites reside within the most hydrophilic regions of the molecule and that the antigenic residues are likely to be organized as beta sheets which loop out from the surface of the molecule. Together, these data and our previous studies support the conclusion that the mar mutations identified by sequence analysis very likely occur within or near the epitope structures themselves. Thus, two highly antigenic regions of gC have now been physically and genetically mapped to well-defined domains of the protein molecule.