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In order to foresee the impact of permafrost thaw on CO 2 emissions by high-latitude rivers, in-situ measurements across a permafrost and climate/vegetation gradient, coupled with assessment of possible physico-chemical and landscape controlling factors are necessary. Here we chose 34 catchments of variable stream order (1 to 9) and watershed size (1 to >10 5  km 2 ) located across a permafrost and biome gradient in the Western Siberian Lowland (WSL), from the permafrost-free southern taiga to the continuous permafrost zone of tundra. Across the south-north transect, maximal CO 2 emissions (2.2 ± 1.1 g C-CO 2 m -2 d -1 ) occurred from rivers of the discontinuous/sporadic permafrost zone, i.e., geographical permafrost thawing boundary. In this transitional zone, fluvial C emission to downstream export ratio was as high as 8.0, which greatly (x 10) exceeded the ratio in the permafrost free and continuous permafrost zones. Such a high evasion at the permafrost thawing front can stem from an optimal combination of multiple environmental factors: maximal active layer thickness, sizable C stock in soils, and mobilization of labile organic nutrients from dispersed peat ice that enhanced DOC and POC processing in the water column, likely due to priming effect. Via a substituting space for time approach, we foresee an increase in CO 2 and CH 4 fluvial evasion in the continuous and discontinuous permafrost zone, which is notably linked to the greening of tundra increases in biomass of the riparian vegetation, river water warming and thermokarst lake formation on the watershed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Humic thermokarst lakes of permafrost peatlands in Western Siberia Lowland (WSL) are major environmental controllers of carbon and nutrient storage in inland waters and greenhouse gases emissions to the atmosphere in the subarctic. In contrast to sizable former research devoted to hydrochemical and hydrobiological (phytoplankton) composition, zooplankton communities of these thermokarst lakes and thaw ponds remain poorly understood, especially along the latitudinal gradient, which is a perfect predictor of permafrost zones. To fill this gap, 69 thermokarst lakes of the WSL were sampled using unprecedented spatial coverage, from continuous to sporadic permafrost zone, in order to assess zooplankton (Cladocera, Copepoda, Rotifera) diversity and abundance across three main open water physiological seasons (spring, summer and autumn). We aimed at assessing the relationship of environmental factors (water column hydrochemistry, nutrients, and phytoplankton parameters) with the abundance and diversity of zooplankton. A total of 74 zooplankton species and taxa were detected, with an average eight taxa per lake/pond. Species richness increased towards the north and reached the maximum in the continuous permafrost zone with 13 species found in this zone only. In contrast, the number of species per waterbody decreased towards the north, which was mainly associated with a decrease in the number of cladocerans. Abundance and diversity of specific zooplankton groups strongly varied across the seasons and permafrost zones. Among the main environmental controllers, Redundancy Analysis revealed that water temperature, lake area, depth, pH, Dissolved Inorganic and Organic Carbon and CO 2 concentrations were closely related to zooplankton abundance. Cladocerans were positively related to water temperature during all seasons. Copepods were positively related to depth and lake water pH in all seasons. Rotifers were related to different factors in each season, but were most strongly associated with DOC, depth, CH 4 , phytoplankton and cladoceran abundance. Under climate warming scenario, considering water temperature increase and permafrost boundary shift northward, one can expect an increase in the diversity and abundance of cladocerans towards the north which can lead to partial disappearance of copepods, especially rare calanoid species., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Despite the importance of small and medium size rivers of Siberian boreal zone in greenhouse gases (GHG) emission, major knowledge gaps exist regarding its temporal variability and controlling mechanisms. Here we sampled 11 pristine rivers of the southern taiga biome (western Siberia Lowland, WSL), ranging in watershed area from 0.8 to 119,000 km 2 , to reveal temporal pattern and examine main environmental controllers of GHG emissions from the river water surfaces. Floating chamber measurements demonstrated that CO 2 emissions from water surface decreased by 2 to 4-folds from spring to summer and autumn, were independent of the size of the watershed and stream order and did not exhibit sizable (>30 %, regardless of season) variations between day and night. The CH 4 concentrations and fluxes increased in the order "spring ≤ summer < autumn" and ranged from 1 to 15 μmol L -1 and 5 to 100 mmol m -2 d -1 , respectively. The CO 2 concentrations and fluxes (range from 100 to 400 μmol L -1 and 1 to 4 g C m -2 d -1 , respectively) were positively correlated with dissolved and particulate organic carbon, total nitrogen and bacterial number of the water column. The CH 4 concentrations and fluxes were positively correlated with phosphate and ammonia concentrations. Of the landscape parameters, positive correlations were detected between riparian vegetation biomass and CO 2 and CH 4 concentrations. Over the six-month open-water period, areal emissions of C (>99.5 % CO 2 ; <0.5 % CH 4 ) from the watersheds of 11 rivers were equal to the total downstream C export in this part of the WSL. Based on correlations between environmental controllers (watershed land cover and the water column parameters), we hypothesize that the fluxes are largely driven by riverine mineralization of terrestrial dissolved and particulate OC, coupled with respiration at the river bottom and riparian sediments. It follows that, under climate warming scenario, most significant changes in GHG regimes of western Siberian rivers located in permafrost-free zone may occur due to changes in the riparian zone vegetation and water coverage of the floodplains., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Shallow thaw (thermokarst) lakes abundant in regions of permafrost-affected peatlands represent important sources of carbon dioxide and methane emission to the atmosphere, however the quantitative parameters of phytoplankton communities which control the C cycle in these lakes remain poorly known. This is especially true considering the roles of permafrost, hydrochemical composition of lakes, lake sizes and season as major governing factors on phytoplankton abundance and biodiversity. In this work, we quantified phytoplankton characteristics of 27 thermokarst lakes (sizes ranging from 115 m2 to 1.24 km 2 ) sampled in spring, summer and autumn across a permafrost gradient (isolated, sporadic, discontinuous and continuous zone) in the Western Siberia Lowland (WSL). The biodiversity indices were highest during all seasons in lakes of the continuous permafrost zone and rather similar in lakes of isolated, sporadic and discontinuous permafrost zone. Considering all seasons and permafrost zones, the biomass and cell number of phytoplankton correlated with Dissolved Organic Carbon (DOC), phosphate, and some metal micro-nutrients (Ni, Zn). The strongest correlations were observed for Cyanophycea during summer, with pH, Ni, Cu, Zn, Sr, Ba (cell number) and Cu, Zn, Ba (biomass), and during autumn, with DOC, K, Cr, Cu, Zn, Ba, Cd, Pb (biomass). Using a substituting space for time approach for climate warming and permafrost thaw and suggesting a shift in permafrost boundaries northward, we foresee an increase in cell number and biomass in continuous permafrost zone in spring and summer, and a decrease in phytoplankton abundance in the discontinuous and sporadic permafrost zones. The biodiversity of phytoplankton in the continuous permafrost zone might decrease whereas in other zones, it may not exhibit any sizably change. However, in case of strong deepening of the active layer down to underlaying mineral horizons, and the release of some limiting nutrients (Si, P) due to enhanced connectivity of the lake with groundwater, the share of cyanobacteria and diatoms may increase., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Permafrost thaw in continental lowlands produces large number of thermokarst (thaw) lakes, which act as a major regulator of carbon (C) storage in sediments and C emission in the atmosphere. Here we studied thaw lakes of the NE European permafrost peatlands - shallow water bodies located within frozen peat bogs and receiving the majority of their water input from lateral (surface) runoff. We also conducted mesocosm experiments via interacting lake waters with frozen peat and dominant ground vegetation - lichen and moss. There was a systematic decrease in concentrations of dissolved C, CO 2 , nutrients and metals with an increase in lake size, corresponding to temporal evolution of the water body and thermokarst development. We hypothesized that ground vegetation and frozen peat provide the majority of C, nutrients and inorganic solutes in the water column of these lakes, and that microbial processing of terrestrial organic matter controls the pattern of CO 2 and nutrient concentrations in thermokarst lakes. Substrate mass-normalized C, nutrient (N, P, K), major and trace metal release was maximal in moss mesocosms. After first 16 h of reaction, the pCO 2 increased ten-fold in mesocosms with moss and lichen; this increase was much less pronounced in experiments with permafrost peat. Overall, moss and lichen were the dominant factors controlling the enrichment of the lake water in organic C, nutrients, and trace metals and rising the CO 2 concentration. The global significance of obtained results is that the changes in ground vegetation, rather than mere frozen peat thawing, may exert the primary control on C, major and trace element balance in aquatic ecosystems of tundra peatlands under climate warming scenario., Competing Interests: Declaration of competing interest We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The chemical composition of thermokarst lake ecosystem components is a crucial indicator of current climate change and permafrost thaw. Despite high importance of macrophytes in shallow permafrost thaw lakes for control of major and trace nutrients in lake water, the trace element (TE) partitioning between macrophytes and lake water and sediments in the permafrost regions remains virtually unknown. Here we sampled dominant macrophytes in thermokarst lakes of discontinuous and continuous permafrost zones in the Western Siberia Lowland (WSL) and measured major and trace elements in plant biomass, lake water, lake sediments and sediment porewater. All six plant species (Hippuris vulgaris L., Glyceria maxima (Hartm.) Holmb., Comarum palustre L., Ranunculus spitzbergensis Hadac, Carex aquatilis Wahlenb s. str., Menyanthes trifoliata L.) sizably accumulated macronutrients (Na, Mg, Ca), micronutrients (B, Mo, Nu, Cu, Zn, Co) and toxicants (As, Cd). Accumulation of other trace elements, including rare earth elements (REE), in macrophytes relative to pore waters and sediments was highly variable among species. Using miltiparametric statistics, we described the behavior of ТЕ across two permafrost zones and identified several group of elements depending on their sources in the lake ecosystems and their affinity to sediments and macrophytes. Under future climate warming and shifting the permafrost border to the north, we anticipate an increasing uptake of heavy metals and lithogenic low mobile elements such as Ti, Al, Cr, As, Cu, Fe, Ni, Ga, Zr, and REEs by macrophytes in the discontinuous permafrost zone and Ba, Zn, Pb and Cd in the continuous permafrost zone. This may eventually diminish transport of metal micronutrients and geochemical tracers from soils to lakes and rivers and further to the Arctic Ocean., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Arctic regions contain large amounts of organic carbon (OC) trapped in soil and wetland permafrost. With climate warming, part of this OC is released to aquatic systems and degraded by microorganisms, thus resulting in positive feedback due to carbon (C) emission. In wetland areas, water bodies are spatially heterogenic and separated by landscape position and water residence time. This represents a hydrological continuum, from depressions, smaller water bodies and lakes to the receiving streams and rivers. Yet, the effect of this heterogeneity on the OC release from the soil and its processing in waters is largely unknown and not accounted for in C cycle models of Arctic regions. Here we investigated the dissolved OC (DOC) biodegradation of aquatic systems along a hydrological continuum located in two discontinuous permafrost sites: in western Siberia and northern Sweden. The biodegradable dissolved OC (BDOC 15 ; % DOC lost relative to the initial DOC concentration after 15 days incubation at 20 °C) ranged from 0 to 20% for small water bodies located at the beginning of the continuum (soil solutions, small ponds, fen and lakes) and from 10 to 20% for streams and rivers. While the BDOC 15 increased, the removal rate of DOC decreased along the hydrological continuum. The potential maximum CO 2 production from DOC biodegradation was estimated to account for only a small part of in-situ CO 2 emissions measured in peatland aquatic systems of northern Sweden and western Siberia. This suggests that other sources, such as sediment respiration and soil input, largely contribute to CO 2 emissions from small surface waters of permafrost peatlands. Our results highlight the need to account for large heterogeneity of dissolved OC concentration and biodegradability in order to quantify C cycling in arctic water bodies susceptible to permafrost thaw., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Despite the importance of surface waters of permafrost landscapes in carbon (C) emission and dissolved C and metal storage and export, the majority of available observations in high latitude aquatic systems deal with punctual or seasonal sampling without accounting for diurnal variations in temperature and primary productivity-respiration cycles. Towards providing comprehensive understanding of diel variations in CO 2 emission, organic C and element concentrations in lakes of frozen peatlands, we monitored, each 2 h over 2 days, the water temperature, pH, CO 2 fluxes, CO 2 , CH 4 , dissolved organic and inorganic carbon (DOC and DIC, respectively), nutrients, carboxylic acids, bacterial number, and major and trace elements in two acidic (pH = 3.6 and 4.0) and humic (DOC = 15 and 35 mg L -1 ) thermokarst lakes of discontinuous permafrost zone in Western Siberia. We discovered a factor of 2 to 3 higher CO 2 concentrations and fluxes during the night compared to daytime in the high-DOC lake. The emission fluxes in the low-DOC lake increased from zero to negative values during the day to highly positive values during the end of night and early morning. The methane concentration varied within a factor of 5 without any link to the diurnal cycle. The bulk of dissolved (< 0.45 μm) hydrochemical parameters remained highly stable with ±10% variation in concentration over 2 days of observation (DOC, DIC, SUVA 254nm , carboxylates (formate, oxalate, puryvate and glutarate), Mn, Fe, Al, other trace elements). Concentrations of Si, P, K, Cu varied within ±20% whereas those of Zn and Ni ranged by a factor of 2 to 4 without any link to diurnal pattern. Overall, the impact of diel cycle on CH 4 , DOC, nutrient and metal concentration was below 10%. However, neglecting night-time period may underestimate net CO 2 emission by ca. 30 to 50% in small organic-rich thaw ponds and switch the CO 2 exchange from uptake/zero to net emission in larger thermokarst lakes. Given the dominance of large lakes in permafrost regions, the global underestimation of the emission flux may be quite high. As such, monitoring CO 2 concentrations and fluxes in thermokarst lakes during months of extended night time (August to October) is mandatory for assessing the net emissions from lentic waters of frozen peatlands., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Soil pore waters are a vital component of the ecosystem as they are efficient tracers of mineral weathering, plant litter leaching, and nutrient uptake by vegetation. In the permafrost environment, maximal hydraulic connectivity and element transport from soils to rivers and lakes occurs via supra-permafrost flow (i.e. water, gases, suspended matter, and solutes migration over the permafrost table). To assess possible consequences of permafrost thaw and climate warming on carbon and Green House gases (GHG) dynamics we used a "substituting space for time" approach in the largest frozen peatland of the world. We sampled stagnant supra-permafrost (active layer) waters in peat columns of western Siberia Lowland (WSL) across substantial gradients of climate (-4.0 to -9.1°C mean annual temperature, 360 to 600mm annual precipitation), active layer thickness (ALT) (>300 to 40cm), and permafrost coverage (sporadic, discontinuous and continuous). We analyzed CO 2 , CH 4 , dissolved carbon, and major and trace elements (TE) in 93 soil pit samples corresponding to several typical micro landscapes constituting the WSL territory (peat mounds, hollows, and permafrost subsidences and depressions). We expected a decrease in intensity of DOC and TE mobilization from soil and vegetation litter to the supra-permafrost water with increasing permafrost coverage, decreasing annual temperature and ALT along a latitudinal transect from 62.3°N to 67.4°N. However, a number of solutes (DOC, CO 2 , alkaline earth metals, Si, trivalent and tetravalent hydrolysates, and micronutrients (Mn, Co, Ni, Cu, V, Mo) exhibited a northward increasing trend with highest concentrations within the continuous permafrost zone. Within the "substituting space for time" climate change scenario and northward shift of the permafrost boundary, our results suggest that CO 2 , DOC, and many major and trace elements will decrease their concentration in soil supra-permafrost waters at the boundary between thaw and frozen layers. As a result, export of DOC and elements from peat soil to lakes and rivers of the WSL (and further to the Arctic Ocean) may decrease., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Photo-induced degradation of dissolved organic matter (DOM) and organo-mineral colloids is one of the major factor responsible for transformation of DOM and dissolved metals in boreal and subarctic waters. In contrast to fairly good understanding of this process in inland waters of high latitude zone, the transformation of riverine DOM and associated trace element (TE) colloids in the Arctic estuaries remains virtually unknown. We incubated, under sunlight in outdoor pools, quartz reactors filled with mixtures of sterile filtered riverine and estuarine water. The water samples were collected in the estuarine zone of the largest European Arctic river, Severnaya Dvina. After 1month of exposure to sunlight, ≤5% change of dissolved organic carbon (DOC) concentration and specific ultraviolet (254nm) absorption occurred. This decrease was within the experimental uncertainty and it implies quite high resistance of river dissolved organic matter to photo-degradation in this estuary. Moreover, very low photodegradability of DOM in the freshwater point of the Severnaya Dvina River may require revisiting the current paradigm of the importance of DOC photolysis in large Arctic rivers. A novel finding was that the percentages of overall removal of Fe and some insoluble elements were quite similar across the full range of studied salinities, whereas the apparent rate of metal removal decreased with the increase of salinity. Overall, the salinity weakly impacted the removal of riverine DOC and metals in the estuarine water via photolysis and coagulation under sunlight. As a result, photoreactivity of DOM and dissolved metals in riverine end members corrected for estuarine dilution can be used to approximate the photolytic transformation of riverine material in the Arctic coastal zone., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The heterotrophic mineralization of dissolved organic matter (DOM) controls the CO 2 flux from the inland waters to the atmosphere, especially in the boreal waters, although the mechanisms of this process and the fate of trace metals associated with DOM remain poorly understood. We studied the interaction of culturable aquatic (Pseudomonas saponiphila) and soil (Pseudomonas aureofaciens) Gammaproteobacteria with seven different organic substrates collected in subarctic settings. These included peat leachate, pine crown throughfall, fen, humic lake, stream, river, and oligotrophic lake with variable dissolved organic carbon (DOC) concentrations (from 4 to 60mgL -1 ). The highest removal of DOC over 4days of reaction was observed in the presence of P. aureofaciens (33±5%, 43±3% and 53±7% of the initial amount in fen water, humic lake and stream, respectively). P. saponiphila degraded only 5% of DOC in fen water but did not affect all other substrates. Trace elements (TE) were essentially controlled by short-term (0-1h) adsorption on the surface of cells. Regardless of the nature of organic substrate and the identity of bacteria, the degree of adsorption ranged from 20 to 60% for iron (Fe 3+ ), 15 to 55% for aluminum (Al), 10 to 60% for manganese (Mn), 10 to 70% for nickel (Ni), 20 to 70% for copper (Cu), 10 to 60% for yttrium (Y), 30 to 80% for rare earth elements (REE), and 15 to 50% for uranium (U VI ). Rapid adsorption of organic and organo-mineral colloids on bacterial cell surfaces is novel and potentially important process, which deserves special investigation. The long-term removal of dissolved Fe and Al was generally consistent with solution supersaturation degree with respect to Fe and Al hydroxides, calculated by visual Minteq model. Overall, the biomass-normalized biodegradability of various allochthonous substrates by culturable bacteria is much lower than that of boreal DOM by natural microbial consortia., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Thaw of frozen peat in discontinuous permafrost zone produces a significant number of thermokarst lakes, which are known to contribute to Green House Gases (GHG) emission in the atmosphere. In palsa peatland of western Siberia, the thermokarst lake formation includes soil subsidences, lichen submergence and peat abrasion, leading to lateral spreading of the lake border, often intensified by ground fires. Mesocosm experiments were conducted during 3weeks on two thermokarst lake waters interacting in 30-L tanks with surface horizon of peat, the dominant ground vegetation (lichen Cladonia sp.) and the ash produced by lichen burning at 450°C. The obtained results allowed a better understanding of physico-chemical factors controlling the enrichment of thermokarst lake water in organic carbon and metals, and evaluating CO 2 sequestration/emission potential. The changes of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC), major element and divalent metal concentration in response to peat and lichen biomass addition were less than a factor of 2 over full duration of the experiment. Iron (Fe) concentration in the lake water decreased by a factor of 2 to 3 after the addition of peat and lichen biomass. The concentration of low-soluble trivalent and tetravalent hydrolysates decreased by ca. 30 to 50%, presumably due to their co-precipitation with Fe hydroxide. The dissolved carbon dioxide (CO 2 ) in tank with lichen increased by a factor of 5.5±0.5, likely due to respiration of algal component in closed environment. Strong enrichment of the lake water in DIC, P, K, Ca, Mg, Si, Al, Ti, Mn, Mo, Rb, As, Sb and U upon the ash addition persisted over full duration of experiments and was significant (p<0.0001) compared to peat and lichen biomass treatments. These elements may serve as indicators of ground fire impact on thermokarst lake water's chemistry. The overall effect of ash leaching on aquatic ecosystems after ground fire of frozen Siberian peatland is predicted to be much stronger than that currently recognized for non-permafrost regions., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The colloidal distribution and size fractionation of organic carbon (OC), major elements and trace elements (TE) were studied in a seasonally stratified, organic-rich boreal lake, Lake Svyatoe, located in the European subarctic zone (NW Russia, Arkhangelsk region). This study took place over the course of 4 years in both winter and summer periods using an in situ dialysis technique (1 kDa, 10 kDa and 50 kDa) and traditional frontal filtration and ultrafiltration (5, 0.22 and 0.025 μm). We observed a systematic difference in dissolved elements and colloidal fractions between summer and winter periods with the highest proportion of organic and organo-ferric colloids (1 kDa-0.22 μm) observed during winter periods. The anomalously hot summer of 2010 in European Russia produced surface water temperatures of approximately 30°C, which were 10° above the usual summer temperatures and brought about crucial changes in element speciation and size fractionation. In August 2010, the concentration of dissolved organic carbon (DOC) decreased by more than 30% compared to normal period, while the relative proportion of organic colloids decreased from 70-80% to only 20-30% over the full depth of the water column. Similarly, the proportion of colloidal Fe decreased from 90-98% in most summers and winters to approximately 60-70% in August 2010. During this hot summer, measurable and significant (>30% compared to other periods) decreases in the colloidal fractions of Ca, Mg, Sr, Ba, Al, Ti, Ni, As, V, Co, Y, all rare earth elements (REEs), Zr, Hf, Th and U were also observed. In addition, dissolved (<0.22 μm) TE concentrations decreased by a factor of 2 to 6 compared to previously investigated periods. The three processes most likely responsible for such a crucial change in element biogeochemistry with elevated water temperature are 1) massive phytoplankton bloom, 2) enhanced mineralization (respiration) of allochthonous dissolved organic matter by heterotrophic aerobic bacterioplankton and 3) photo-degradation of DOM and photo-chemical liberation of organic-bound TE. While the first process may have caused significant decreases in the total dissolved concentration of micronutrients (a factor of 2 to 5 for Cr, Mn, Fe, Ni, Cu, Zn and Cd and a factor of >100 for Co), the second and third factors could have brought about the decrease of allochthonous DOC concentration as well as the concentration and proportion of organic and organo-mineral colloidal forms of non-essential low-soluble trace elements present in the form of organic colloids (Al, Y, Ti, Zr, Hf, Th, Pb, all REEs). It can be hypothesized that climate warming in high latitudes capable of significantly raising surface water temperatures will produce a decrease in the colloidal fraction of most trace elements and, as a result, an increase in the most labile low molecular weight LMW(<1 kDa) fraction., (Copyright © 2013 Elsevier B.V. All rights reserved.)