A.A. Starikova

Features of proteolytic properties of tetraphenylporphyrin complex with lanthanide group metals

Demetallation of metalloporphyrin molecules is one of the essential degradation reactions in photosynthesis. The effect of metalloporphyrin nature on removal of central metals from tetraphenylporphyrin complexes based on lanthanide group metals (Dy, Er, Lu, Ho) has been studied. pH values, at which the metal ions leave the metalloporphyrin complex were established using two-phase spectrophotometric titration with potentiometric pH-control. The pH values decrease with the increase of atomic numbers of lanthanide groups, as well as with increase of 4f-electrons. The reaction of an extra ligand exchange for the hydroxide ion was studied. For Dy-, Er- and Ho-tetraphenylporphyrin complexes one particle of extra ligand coordinates with one porphyrin complex. A complex with dimeric particles can be formed for the system of Lu-tetraphenylporphyrin. Constants of the ion exchange reactions were calculated.nnnSYNOPSISnThe effect of metalloporphyrin nature on removal of central metals from tetraphenylporphyrin complexes based on lanthanide group metals (Dy, Er, Lu, Ho) has been studied. The heterophase reaction of ion-selective electrodes were calculated, as well as the reaction of an extra ligand exchange for the hydroxide ion.

Towards stabilization of the potential response of Mn(III) tetraphenylporphyrin-based solid-state electrodes with selectivity for salicylate ions

AbstractWe report a new type of solid-state electrode (type I) of a simple design with polyvinyl chloride membranes based on Mn(III) tetraphenylporphyrin and with graphite as the electronically conducting substrate. Enlargement of the membrane/graphite contact area by soaking graphite in the plasticizer with subsequent conditioning of the electrode at 30xa0°C allowed us to shorten the time required to achieve steady potential values of the sensors to just 3xa0days. These electrodes do not require a specially added RedOx system in the transducer layer. Stabilization of the EMF response of type I electrodes is compared to type II electrodes which contain a Cu0/Cu2+ RedOx couple in the transducer layer. Type I sensors are suitable for measuring the salicylate ion concentration in the clinically important concentration range down to 2.5xa0×xa010−4xa0M with a sensitivity to salicylate ion of −59.0xa0mV decade−1 in solutions with a high constant background of chloride ions of 0.12xa0M at pHxa0=xa05.3, making this a promising technique for an effective design of solid-contact ion-selective electrodes with polymeric sensing membranes.n Graphical abstractᅟ

Response of Landscapes of the Sikhote-Alin Western Slopes to the Middle–Late Holocene Climatic Changes

The response of landscape biotic components of the western slope of the Sikhote-Alin Mountains (Bikin River middle flow) to the Middle–Late Holocene climate changes is discussed. The paleoreconstruction object was the Krasny Yar mari, which developed under the control of multidirectional short-term climatic changes. The last millennium was marked by particularly rapid and frequent changes in the local landscapes. The closely spaced orographic barrier strongly affected the development of biotic components and changes in the swamp hydrological regime. The moisture dynamics within the river catchment considerably controlled the development and change of the peat-forming plants. Several stages of the mari development were reconstructed; each began from the accumulation of eutrophic peat. It was followed by the transitional eutrophic–mesotrophic stage, with a higher role of atmospheric supply. The larch forests appeared in this part of the valley within the Atlantic–Subboreal cooling period. Korean pine developed in the forest vegetation in the low mountain relief at the beginning of the Subboreal and became one of the leading trees ~2.6–2.3 ka BP. The lower role of the Korean pine and birch forest expansion in the first half of the Subatlantic could be related to the fires. The broadleaf–Korean pine forests became widespread in the Medieval Warm Period. Local swamp landscapes changed dramatically in the Little Ice Age, while the slope vegetation was not subject to any major changes. The landscapes were also affected by the fires, which became more frequent. The derivative communities with birch appeared on the mari. Moreover, this part of the valley was occasionally subject to heavy flooding.

U–Th age of the Kazantsevo (MIS 5) Horizon of the Upper Neopleistocene Ust Oda reference section, Baikal Region

For the first time, the organic sediments of the Kazantsevo Horizon (Baikal Region) were characterized geochronometrically. The 230Th/U age of the buried gyttias from the Upper Neopleistocene Ust Oda stratotypical section on the Kitoi River was determined using a new version of isochronous approximation. The assemblage of all the 230Th/U age data, which were obtained taking into account the errors in the entire range from 136 to 86 kyr, indicates that most likely gyttia age is 115–104 kyr (MIS 5d). Thus, the paleontological conclusions on the Kazantsevo age of the Ust Oda Formation with buried gyttias are confirmed. Our geochronometric data supplement and make more reliable the age model of the formation of sedimentary rocks of the Ust Oda section.

Chronostratigraphy of the Cheremoshnik key section (Yaroslavl Volga region) based on new geochronological, palynological, and paleosol data

According to radiochemical and biostratigraphic studies of the buried peat layer in the Cheremoshnik key section on the East European plain, the first age dating of this peat was obtained and its assignment to the Mikulino interglacial was confirmed. The Th/U isotope age data obtained for the peat horizon allow us to state with confidence that it was formed during the MIS5e. It was found that a variety of signs, including the lithological characteristics of dated layers and climatic indexes, is evidence that the Cheremoshnik site and Borisoglebsk upland occurred in the periglacial zone during MIS3–MIS2.