scholarly journals Molecular foundations of Precambrian uniformitarianism

2021 ◽  
Author(s):  
Mateusz Kedzior ◽  
Amanda K. Garcia ◽  
Meng Li ◽  
Arnaud Taton ◽  
Zachary R. Adam ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Isotope Fractionation ◽  
Atmospheric Composition ◽  
Rubisco Activity ◽  
Deep Time ◽  
Carbon Isotopic ◽  
Living Organisms ◽  
Geologic Record ◽  
And Control ◽  
Ambient Levels

Uniformitarian assumptions underlie the oldest evidence for living organisms on Earth, the distinct isotope fractionation between inorganic and organic carbon. Aside from a handful of compelling deviations, the 13C/12C isotopic mean of preserved organic carbon (δ13Corg) has remained remarkably unchanged through time. RuBisCO is the principal carboxylase/oxygenase biomolecular component that is thought to primarily account for the generation of these distinct carbon isotopic signals. However, it is difficult to reconcile a mostly unchanging mean δ13Corg with several known factors that can affect the isotope fractionation of RuBisCO, such as atmospheric composition and the amino acid composition of the enzyme itself, which have each changed markedly over Earth history. Here we report the resurrection and genetic incorporation of a Precambrian-age, Form IB RuBisCO in a modern cyanobacterial host. The isotopic composition of biomass relative to CO2 (ϵp) in ancestral and control strains were much greater when grown under Precambrian CO2 concentrations compared to modern ambient levels, but displaying values within a nominal envelope of modern-day RuBisCO IB enzyme variants. We infer that these isotopic differences derive indirectly from the decreased fitness of the AncIB strain, which includes diminished growth capacity and total cell RuBisCO activity. We argue that to answer the greatest questions of deep-time paleobiology, ancient biogeochemical signals should be reproduced in the laboratory through the synthesis of the geologic record with experimentally-derived constraints on underlying ancient molecular biology.

scholarly journals Mechanisms Applied by Protein Inhibitors to Inhibit Cysteine Proteases

2021 ◽  
Vol 22 (3) ◽  
pp. 997
Author(s):  
Livija Tušar ◽  
Aleksandra Usenik ◽  
Boris Turk ◽  
Dušan Turk
Keyword(s):  
Binding Site ◽  
Structural Information ◽  
General Rule ◽  
Structural Data ◽  
Cysteine Proteases ◽  
Protein Inhibitors ◽  
Active Site Cleft ◽  
Living Organisms ◽  
And Control ◽  
Binding Mechanisms

Protein inhibitors of proteases are an important tool of nature to regulate and control proteolysis in living organisms under physiological and pathological conditions. In this review, we analyzed the mechanisms of inhibition of cysteine proteases on the basis of structural information and compiled kinetic data. The gathered structural data indicate that the protein fold is not a major obstacle for the evolution of a protease inhibitor. It appears that nature can convert almost any starting fold into an inhibitor of a protease. In addition, there appears to be no general rule governing the inhibitory mechanism. The structural data make it clear that the “lock and key” mechanism is a historical concept with limited validity. However, the analysis suggests that the shape of the active site cleft of proteases imposes some restraints. When the S1 binding site is shaped as a pocket buried in the structure of protease, inhibitors can apply substrate-like binding mechanisms. In contrast, when the S1 binding site is in part exposed to solvent, the substrate-like inhibition cannot be employed. It appears that all proteases, with the exception of papain-like proteases, belong to the first group of proteases. Finally, we show a number of examples and provide hints on how to engineer protein inhibitors.

EXAMINING EFFECT OF ANIMATION APPLICATIONS ON STUDENT ACHIEVEMENT IN SCIENCE AND TECHNOLOGY COURSE

2015 ◽  
Author(s):  
Sedat Yüksel ◽  
◽  
Mestan Boyaci ◽  
Keyword(s):  
Academic Achievement ◽  
Student Achievement ◽  
Science And Technology ◽  
Control Group ◽  
Constructivist Approach ◽  
8Th Grade ◽  
Living Organisms ◽  
And Control ◽  
Experimental Group ◽  
Technology Course

The aim of this study was to determine whether or not animation applications affect student achievement in science and technology course. For this purpose, effect of constructive approach supported by animations in the instruction of the unit “Living Organisms and Energy” to the 8th grade students on their academic achievement was investigated. This unit was taught to the experimental group using a constructivist approach supported by animations and to the control group using a constructivist approach without animations. For data collection, an achievement was developed and administered to experimental and control groups as pre-tests and post-tests. Collected data was analyzed using t-test and MANOVA. As a result of the research, it was revealed that supporting the constructivist approach with animations was more effective in increasing academic achievement. Key wordThe aim of this study was to determine whether or not animation applications affect student achievement in science and technology course. For this purpose, effect of constructive approach supported by animations in the instruction of the unit “Living Organisms and Energy” to the 8th grade students on their academic achievement was investigated. This unit was taught to the experimental group using a constructivist approach supported by animations and to the control group using a constructivist approach without animations. For data collection, an achievement was developed and administered to experimental and control groups as pre-tests and post-tests. Collected data was analyzed using t-test and MANOVA. As a result of the research, it was revealed that supporting the constructivist approach with animations was more effective in increasing academic achievement. Key words: animation, constructivist science education, teaching supported by computer. s: animation, constructivist science education, teaching supported by computer.

scholarly journals Introduction of Sorghum (Sorghum bicolor (L.) Moench) green manure in rotations of head salads and baby leaf crops under greenhouse

2016 ◽  
Vol 11 ◽  
Author(s):  
Luigi Morra ◽  
Domenico Cerrato ◽  
Maurizio Bilotto ◽  
Salvatore Baiano
Keyword(s):  
Organic Carbon ◽  
Total Nitrogen ◽  
Green Manure ◽  
Soil C ◽  
C Balance ◽  
Soil Biomass ◽  
Starting Point ◽  
Dry Biomass ◽  
One Year ◽  
And Control

This paper deals with the introduction in tunnel-greenhouses of sweet sorghum cultivated in short, summer cycle as green manure with the aim to amend soils with biomass grown on farm. This practice has been spreading in tunnels of Sele river Valley (Salerno, Italy) where baby leaf crops are cultivated in numerous cycles (up to 5-7) per year. Three sorghum varieties for forage or biomass (Goliath, BMR 201 and BMR 333) were cultivated in two farms at Eboli and San Marzano sul Sarno with the aims to study their responses in term of fresh and dry aboveground biomass yielded, C and N content of the biomass incorporated in soil, C balance in amended soils after one year of ordinary cash crop sequences. No differences, with regard to all the parameters measured, were pointed out among the tested varieties in each site. The sorghum cycle lasted 45 days at Eboli, yielding on average 98 and 13 t ha<sup>-1</sup> of fresh and dry biomass, respectively; soil biomass incorporation supplied, on average 5.8 t ha<sup>-1</sup> of organic carbon and 273 kg ha<sup>-1</sup> of total nitrogen. In the farm of San Marzano, sorghum cycle lasted 68 days, yielding 116 and 18 t ha<sup>-1</sup> of fresh and dry biomass, respectively; soil biomass incorporation supplied, on average 8 t ha<sup>-1</sup> of organic carbon and 372 kg ha<sup>-1</sup> of total nitrogen. After one year, the plots amended with sorghum biomass showed a soil organic carbon (SOC) concentration not different from the starting point while SOC decreased in fallow plots. At Eboli, initial SOC content was 12.3 g kg<sup>-1</sup>, but one year later it resulted 12.3, 12.8, 12.2 and 11.3 g kg<sup>-1</sup> in BMR 201, BMR 333, Goliath and control plots, respectively. At San Marzano initial SOC content was 11.4 g kg<sup>-1</sup>, but one year later it resulted 11, 12, 10.7 and 10.5 g kg<sup>-1</sup> in BMR 201, BMR 333, Goliath and control plots, respectively. The annual C balance put in evidence that the green manure with sorghum biomass caused SOC losses higher than those detected in fallow plots let us supposing a prime effect in boosting the soil microbial C mineralization. Only cv BMR 333 in the Eboli trial, pointed out a positive SOC change of 1.8 t ha<sup>-1</sup>. Further studies are requested to better understand the real efficacy of sorghum cover crop in soil amendment under tunnels devoted to intensive vegetable crop sequence.

scholarly journals Spatial distribution and sources of organic carbon in the surface sediment of the Bosten Lake, China

2015 ◽  
Vol 12 (16) ◽  
pp. 13793-13817 ◽  
Author(s):  
Z. T. Yu ◽  
X. J. Wang ◽  
E. L. Zhang ◽  
C. Y. Zhao ◽  
H. Y. Lan
Keyword(s):  
Spatial Distribution ◽  
Organic Carbon ◽  
Energy Levels ◽  
Carbon Isotopic Composition ◽  
Bosten Lake ◽  
Carbon Isotopic ◽  
Complex Processes ◽  
High Kinetic Energy ◽  
Carbon Reservoir ◽  
Kaidu River

Abstract. Lake sediment is an important carbon reservoir. However, little is known on the dynamics and sources of sediment organic carbon in the Bosten Lake. We collected 13 surface (0–2 cm) sediment samples in the Bosten Lake and analyzed total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition in TOC (δ13Corg) and grain size. We found a large spatial variability in TOC content (1.8–4.4 %) and δ13Corg value (−26.77 to −23.98 ‰). Using a three end member mixing model with measured TOC : TN ratio and δ13Corg, we estimated that 54–90 % of TOC was from autochthonous sources. Higher TOC content (> 3.7 %) was found in the east and central-north sections and near the mouth of the Kaidu River, which was attributable to allochthonous, autochthonous plus allochthonous, and autochthonous sources, respectively. The lowest TOC content was found in the mid-west section, which might be a result of high kinetic energy levels. Our study indicated that the spatial distribution of sediment TOC in the Bosten Lake was influenced by multiple and complex processes.

scholarly journals Paleoenvironmental Interpretations on Organic Carbon Isotopic Records from Lake Sediments:A Critique

2001 ◽  
Vol 13 (1) ◽  
pp. 72-78 ◽  
Author(s):  
YU Junqing ◽  
◽  
WANG Xiaoy an ◽  
LI Jun ◽  
AN Zhisheng
Keyword(s):  
Organic Carbon ◽  
Carbon Isotopic ◽  
Isotopic Records

scholarly journals Diurnal variations of organic molecular tracers and stable carbon isotopic compositions in atmospheric aerosols over Mt. Tai in North China Plain: an influence of biomass burning

2012 ◽  
Vol 12 (4) ◽  
pp. 9079-9124
Author(s):  
P. Q. Fu ◽  
K. Kawamura ◽  
J. Chen ◽  
J. Li ◽  
Y. L. Sun ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Biomass Burning ◽  
North China Plain ◽  
North China ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Total Carbon ◽  
Stable Carbon ◽  
Isotopic Compositions ◽  
Carbon Isotopic

Abstract. Organic tracer compounds of tropospheric aerosols, as well as organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and stable carbon isotope ratios (δ13C) of total carbon (TC) have been investigated for aerosol samples collected during early and late periods of Mount Tai eXperiment 2006 (MTX2006) field campaign in North China Plain. Total solvent extracts were investigated by gas chromatography/mass spectrometry. More than 130 organic compounds were detected in the aerosol samples. They were grouped into twelve organic compound classes, including biomass burning tracers, biogenic primary sugars, biogenic secondary organic aerosol (SOA) tracers, and anthropogenic tracers such as phthalates, hopanes and polycyclic aromatic hydrocarbons (PAHs). In early June when the field burning activities of wheat straws in North China Plain were very active, the total identified organics (2090 ± 1170 ng m−3) were double those in late June (926 ± 574 ng m−3). All the compound classes were more abundant in early June than in late June, except phthalate esters, which were higher in late June. Levoglucosan (88–1210 ng m−3, 403 ng m−3) was found as the most abundant single compound in early June, while diisobutyl phthalate was the predominant species in late June. During the biomass-burning period in early June, the diurnal trends of most of the primary and secondary organic aerosol tracers were characterized by the concentration peaks observed at mid-night or in early morning, while in late June most of the organic species peaked in late afternoon. This suggests that smoke plumes from biomass burning can uplift the aerosol particulate matter to a certain altitude and then transported to and encountered the summit of Mt. Tai during nighttime. On the basis of the tracer-based method for the estimation of biomass-burning OC, fungal-spore OC and biogenic secondary organic carbon (SOC), we estimate that an average of 24% (up to 64%) of the OC in the Mt. Tai aerosols was due to biomass burning in early June, followed by the contribution of isoprene SOC (mean 4.3%). In contrast, isoprene SOC was the main contributor (6.6%) to OC, and only 3.0% of the OC was due to biomass burning in late June. In early June, δ13C of TC (−26.6‰ to −23.2‰, mean −25.0‰) were lower than those (−23.9‰ to −21.9‰, mean −22.9‰) in late June. In addition, a strong anti-correlation was found between levoglucosan and δ13C values. This study demonstrates that crop-residue burning activities can significantly enhance the organic aerosol loading and alter the organic molecular compositions and stable carbon isotopic compositions of aerosol particles in the troposphere over North China Plain.

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