The approach involved recording the steady-state current for FeIII reduction at a 25 microm diameter disc-shaped ultramicroelectrode UME positioned close to the fibre  https//enwikipediaorg/wiki/SNAC  in the light flux through the fibre off-on was then applied which led to a depletion in the local FeIII concentration The resulting chronoamperometric behaviour at the UME, as a consequence of the solution photochemical process, was measured A theoretical model has been developed to simulate experimental current-time profiles, which enabled measurements of the light flux initiating Woodward-Hoffmann rules in density functional theory initial hardness responseWetenschappen, Pleinlaan 2, 1050 Brussels, BelgiumThe Woodward-Hoffmann rules for pericyclic reactions, a fundamental set of reactivity rules in organic chemistry, are formulated in the language of conceptual density functional theory DFT
 
  DFT provides an elegant framework to introduce chemical concepts and principles in a quantitative manner, partly because it is formulated without explicit reference to a wave function, on whose symmetry properties the Woodward-Hoffmann [J Am Chem Soc 87, 395 1965] rules are based We have studied the initial chemical hardness response using a model reaction profile for two prototypical pericyclic reactions, the Diels-Alder cycloaddition of 1,3-butadiene to ethylene and the addition of ethylene to ethylene, both in the singlet ground state and in the first triplet excited state For the reaction that is thermally allowed but photochemically forbidden, the initial hardness response is positive along the singlet reaction profile
 
  By contrast, for the triplet reaction profile, a negative hardness response is observed For the photochemically allowed, thermally forbidden reaction, the behavior of the chemical hardness along the initial stages of the singlet and triplet reaction profiles is reversed This constitutes a first step in showing that chemical concepts from DFT can be invoked to explain results that would otherwise require invoking the phase of the wave functionIn Situ, Protein-Mediated Generation of a Photochemically Active Chlorophyll Analogue in a Mutant Bacterial Photosynthetic Reaction CenterAll possible natural amino acids have been substituted for the native LeuL185 positioned near the B-side bacteriopheophytin HB in the bacterial reaction center RC from Rhodobacter sphaeroides Additional mutations that enhance electron transfer to the normally inactive B-side cofactors are present Approximately half of the isolated RCs with Glu at L185 contain a magnesium chlorin CB in place of HB
 
  The chlorin is not the common BChl a oxidation product 3-desvinyl-3-acetyl chlorophyll a with a C-C bond in ring D and a C═C bond in ring B but has properties consistent with reversal of these bond orders, giving 17,18-didehydro BChl a In such RCs, charge-separated state P+CB- forms in ∼5 yield The other half of the GluL185-containing RCs have a bacteriochlorophyll a BChl a denoted βB in place of HB Residues His, Asp, Asn, and Gln at L185 yield RCs with ≥85 βB in the HB site, while most other amino acids result in RCs that retain HB ≥95 To the best of our knowledge, neither bacterial RCs that harbor five BChl a molecules and one chlorophyll analogue nor those with six BChl a molecules have been reported previously The finding that altering the local environment within a cofactor binding site of a transmembrane complex leads to in situ generation of a photoactive chlorin with an unusual ring oxidation pattern suggests new strategies for amino acid control over pigment type at specific sites in photosynthetic proteinsAn inevitable but underestimated photoaging behavior of plastic waste in the aquatic environment Critical role of nitrate
 
 Lake, Ministry of Education, College of Environment, Hohai University, Nanjing, Lake, Ministry of Education, College of Environment, Hohai University, Nanjing, Photoaging is an important reaction for waste plastics in the aquatic environment and plays a key role in the lifetime of plastics Nevertheless, when natural photosensitive substances such as nitrate participate in this process, the physiochemical changes in plastics and the corresponding reaction mechanisms are not well-understood In this work, the photochemical behavior of polyethylene terephthalate PET bottles in deionized water and nitrate solution was systematically investigated under ultraviolet UV irradiation The analyses of the surface physicochemical properties of the photoaged PET bottles indicated that, after 20 days of photo-irradiation, the presence of nitrate reduced the contact angle from 69nbsp;±nbsp;0° to 60nbsp;±nbsp;0°, and increased the O/C ratio from 03 to 02, respectively  http//wwwallinnocom/product/cyclodextrin/683html  leaching rate of dissolved organic carbon DOC, which was 0193nbsp;mgnbsp;g-1·day-1 in nitrate solution, was twice that of 00941nbsp;mgnbsp;g-1·day-1 in deionized water Furthermore, fluorescence spectroscopy revealed that the increasing DOC had aromatic rings with hydroxyl on the side-chain formed after UV irradiation