TY - JOUR A1 - Riedel, M. A1 - Sabir, N. A1 - Scheller, Frieder W. A1 - Parak, Wolfgang J. A1 - Lisdat, Fred T1 - Connecting quantum dots with enzymes BT - mediator-based approaches for the light-directed read-out of glucose and fructose oxidation JF - Nanoscale N2 - The combination of the biocatalytic features of enzymes with the unique physical properties of nanoparticles in a biohybrid system provides a promising approach for the development of advanced bioelectrocatalytic devices. This study describes the construction of photoelectrochemical signal chains based on CdSe/ZnS quantum dot (QD) modified gold electrodes as light switchable elements, and low molecular weight redox molecules for the combination with different biocatalysts. Photoelectrochemical and photoluminescence experiments verify that electron transfer can be achieved between the redox molecules hexacyanoferrate and ferrocene, and the QDs under illumination. Since for both redox mediators a concentration dependent photocurrent change has been found, light switchable enzymatic signal chains are built up with fructose dehydrogenase (FDH) and pyrroloquinoline quinone-dependent glucose dehydrogenase ((PQQ) GDH) for the detection of sugars. After immobilization of the enzymes at the QD electrode the biocatalytic oxidation of the substrates can be followed by conversion of the redox mediator in solution and subsequent detection at the QD electrode. Furthermore, (PQQ) GDH has been assembled together with ferrocenecarboxylic acid on top of the QD electrode for the construction of a funtional biohybrid architecture, showing that electron transfer can be realized from the enzyme over the redox mediator to the QDs and subsequently to the electrode in a completely immobilized fashion. The results obtained here do not only provide the basis for light-switchable biosensing and bioelectrocatalytic applications, but may also open the way for self-driven point-of-care systems by combination with solar cell approaches (power generation at the QD electrode by enzymatic substrate consumption). Y1 - 2017 U6 - https://doi.org/10.1039/c7nr00091j SN - 2040-3364 SN - 2040-3372 VL - 9 SP - 2814 EP - 2823 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Basavaiah, Nathani A1 - Wiesner, M. G. A1 - Anoop, Ambili A1 - Menzel, P. A1 - Nowaczyk, Norbert R. A1 - Deenadayalan, K. A1 - Brauer, Achim A1 - Gaye, Birgit A1 - Naumann, R. A1 - Riedel, N. A1 - Stebich, M. A1 - Prasad, Sushma T1 - Physicochemical analyses of surface sediments from the Lonar Lake, central India - implications for palaeoenvironmental reconstruction JF - Fundamental and applied limnology : official journal of the International Association of Theoretical and Applied Limnology N2 - We report the results of our investigations on the catchment area, surface sediments, and hydrology of the monsoonal Lonar Lake, central India. Our results indicate that the lake is currently stratified with an anoxic bottom layer, and there is a spatial heterogeneity in the sensitivity of sediment parameters to different environmental processes. In the shallow (0-5 m) near shore oxic-suboxic environments the lithogenic and terrestrial organic content is high and spatially variable, and the organics show degradation in the oxic part. Due to aerial exposure resulting from lake level changes of at least 3m, the evaporitic carbonates are not completely preserved. In the deep water (>5 m) anoxic environment the lithogenics are uniformly distributed and the delta C-13 is an indicator not only for aquatic vs. terrestrial plants but also of lake pH and salinity. The isotopic composition of the evaporites is dependent not only on the isotopic composition of source water (monsoon rainfall and stream inflow) and evaporation, but is also influenced by proximity to the isotopically depleted stream inflow. We conclude that in the deep water environment lithogenic content, and isotopic composition of organic matter can be used for palaeoenvironmental reconstruction. KW - isotopes KW - lonar lake KW - modern surface sediments KW - magnetic parameters KW - monsoon KW - palaeoenvironmental proxies Y1 - 2014 U6 - https://doi.org/10.1127/1863-9135/2014/0515 SN - 1863-9135 VL - 184 IS - 1 SP - 51 EP - 68 PB - Schweizerbart CY - Stuttgart ER - TY - JOUR A1 - Prasad, Sushma A1 - Anoop, A. A1 - Riedel, N. A1 - Sarkar, Saswati A1 - Menzel, P. A1 - Basavaiah, Nathani A1 - Krishnan, R. A1 - Fuller, D. A1 - Plessen, Birgit A1 - Gaye, B. A1 - Roehl, U. A1 - Wilkes, H. A1 - Sachse, Dirk A1 - Sawant, R. A1 - Wiesner, M. G. A1 - Stebich, M. T1 - Prolonged monsoon droughts and links to Indo-Pacific warm pool: A Holocene record from Lonar Lake, central India JF - Earth & planetary science letters N2 - Concerns about the regional impact of global climate change in a warming scenario have highlighted the gaps in our understanding of the Indian Summer Monsoon (ISM, also referred to as the Indian Ocean summer monsoon) and the absence of long term palaeoclimate data from the central Indian core monsoon zone (CMZ). Here we present the first high resolution, well-dated, multiproxy reconstruction of Holocene palaeoclimate from a 10 m long sediment core raised from the Lonar Lake in central India. We show that while the early Holocene onset of-intensified monsoon in the CMZ is similar to that reported from other ISM records, the Lonar data shows two prolonged droughts (PD, multidecadal to centennial periods of weaker monsoon) between 4.6-3.9 and 2-0.6 cal ka. A comparison of our record with available data from other ISM influenced sites shows that the impact of these PD was observed in varying degrees throughout the ISM realm and coincides with intervals of higher solar irradiance. We demonstrate that (i) the regional warming in the Indo-Pacific Warm Pool (IPWP) plays an important role in causing ISM PD through changes in meridional overturning circulation and position of the anomalous Walker cell; (ii) the long term influence of conditions like El Nino-Southern Oscillation (ENSO) on the ISM began only ca. 2 cal ka BP and is coincident with the warming of the southern IPWP; (iii) the first settlements in central India coincided with the onset of the first PD and agricultural populations flourished between the two PD, highlighting the significance of natural climate variability and PD as major environmental factors affecting human settlements. KW - Indian summer monsoon KW - ENSO KW - prolonged droughts KW - Holocene KW - Lonar Lake Y1 - 2014 U6 - https://doi.org/10.1016/j.epsl.2014.01.043 SN - 0012-821X SN - 1385-013X VL - 391 SP - 171 EP - 182 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mishra, Praveen Kumar A1 - Prasad, Sushma A1 - Marwan, Norbert A1 - Anoop, A. A1 - Krishnan, R. A1 - Gaye, Birgit A1 - Basavaiah, N. A1 - Stebich, Martina A1 - Menzel, Philip A1 - Riedel, Nils T1 - Contrasting pattern of hydrological changes during the past two millennia from central and northern India BT - regional climate difference or anthropogenic impact? JF - Global and planetary change N2 - High resolution reconstructions of the India Summer Monsoon (ISM) are essential to identify regionally different patterns of climate change and refine predictive models. We find opposing trends of hydrological proxies between northern (Sahiya cave stalagmite) and central India (Lonar Lake) between 100 and 1300 CE with the strongest anti-correlation between 810 and 1300 CE. The apparently contradictory data raise the question if these are related to widely different regional precipitation patterns or reflect human influence in/around the Lonar Lake. By comparing multiproxy data with historical records, we demonstrate that only the organic proxies in the Lonar Lake show evidence of anthropogenic impact. However, evaporite data (mineralogy and delta O-18) are indicative of precipitation/evaporation (P/E) into the Lonar Lake. Back-trajectories of air-mass circulation over northern and central India show that the relative contribution of the Bay of Bengal (BoB) branch of the ISM is crucial for determining the delta O-18 of carbonate proxies only in north India, whereas central India is affected significantly by the Arabian Sea (AS) branch of the ISM. We conclude that the delta O-18 of evaporative carbonates in the Lonar Lake reflects P/E and, in the interval under consideration, is not influenced by source water changes. The opposing trend between central and northern India can be explained by (i) persistent multidecadal droughts over central India between 810 and 1300 CE that provided an effective mechanism for strengthening sub-tropical westerly winds resulting in enhancement of wintertime (non-monsoonal) rainfall over northern parts of the Indian subcontinent, and/or (ii) increased moisture influx to northern India from the depleted BoB source waters. KW - ENSO KW - Isotopes KW - Indian summer monsoon KW - Lonar Lake KW - Stalagmites KW - Westerlies Y1 - 2017 U6 - https://doi.org/10.1016/j.gloplacha.2017.12.005 SN - 0921-8181 SN - 1872-6364 VL - 161 SP - 97 EP - 107 PB - Elsevier CY - Amsterdam ER -