Mirror-image dependence : targeting enantiomeric G-quadruplex DNA using triplex metallohelices

Natural d‐DNA and l‐DNA are mirror‐image counterparts. However, because of the inherent flexibility and conformation diversity of DNA, it is still not clear how enantiomeric compounds recognize d‐DNA and l‐DNA. Herein, taking G‐quadruplex (G4) DNA as an example that has diverse conformations and distinct biofunctions, the binding of ten pairs of iron triplex metallohelices to d‐ and l‐G4 DNA were evaluated. The Δ‐enantiomer binds to d‐DNA and the Λ‐enantiomer binds to l‐DNA, exhibiting almost the same stabilization effect and binding affinity. The binding affinity of the Δ‐metallohelix with d‐G4 is nearly 70‐fold higher than that of Λ‐metallohelix binding d‐G4. Δ‐Metallohelix binding to d‐G4 follows a two‐step binding process driven by a favorable enthalpy contribution to compensate for the associated unfavorable entropy

Conformation of hydrogen in deep earth

【Abstract】Hydrogen is the simplest atom and the most abundant element in the universe.Molecular hydrogen is a common form of hydrogen,The phase transition of molecular hydrogen at the ultrahigh pressure is the subject of great theoretical and experimental interest in the 1980's.However,whether there exists molecular hydrogen in deep earth is an important problem.This paper presents our recent results

Can Small Industrial Platforms Achieve Large Space Spillover? Identifying the Spatial Spillover Scope of Characteristic Towns Using the Gradient Difference Method

Characteristic towns represent relatively small industrial platforms, characterized by clear industrial positioning, cultural connotations, tourism, and certain community functions. Determining the spatial spillover scope of characteristic towns is of importance for both spatial decision-making and policy optimization. By using the gradient difference method, this paper aims to determine the spatial spillover scope of characteristic towns in 2014 and 2020. The research is based on the nighttime light data of the first three batches of Zhejiang characteristic towns. The results suggest that (1) there is a spatial spillover phenomenon in Zhejiang characteristic towns; namely, the results of 84 characteristic towns are either consistent or partially consistent with the expected results; (2) there is an inverse S-shaped decreasing trend from the boundary of characteristic towns; the trend rapidly decreases with an increase at the boundary distance of characteristic towns; and (3) characteristic towns are formed around the 1 km core spillover area and 2 km secondary spillover area. Provincial characteristic towns have relatively high maturity and account for 43.86% of the total. They are concentrated in the 1 km range. Compared to previous research, this study was able to accurately identify the spatial spillover scope of characteristic towns using the gradient difference method. Specifically, the spatial spillover scope is concentrated primarily in the core spillover area of 1 km. These findings serve as reference for the adjustment and optimization of characteristic town policies as well as of town’s spatial layouts

Effect of detoxification methods on ABE production from corn stover hydrolysate by Clostridium acetobutylicum CICC 8016

In this study, effects of different single biomass derived inhibitors on acetone–butanol–ethanol (ABE) production by Clostridium acetobutylicum CICC 8016 were first investigated. The results showed that formic acid, coumaric acid, and furfural at 0.5 g/L (sodium formate equivalent) inhibited ABE production. Furthermore, corn stover hydrolysate media were prepared following dilute acid pretreatment, enzymatic hydrolysis, and detoxification with different methods. Among overliming, steam stripping, acetone–ethyl ether extraction, and ion exchange with five anion resins, adsorption with resin D301 showed the highest efficiency for inhibitor removal (99–100% of phenolics and 87–99% of sugar degradation products). Without detoxification, ABE production was lower than 1.0 g/L from 28.1 g/L sugars whereas ABE production with medium detoxified by D301 resin achieved higher ABE concentrations and yields than control with synthetic medium. Correlation analysis further revealed that formic acid, coumaric acid, and total phenolics were the major compounds inhibiting ABE production. The results also showed that the single detoxification method was sufficient to detoxify the hydrolysate for ABE production at the pretreatment conditions used in this study.</p

Reassessment of the Role of CaCO3 in n-Butanol Production from Pretreated Lignocellulosic Biomass by Clostridium acetobutylicum

In this study, the role of CaCO3 in n-butanol production was further investigated using corn straw hydrolysate (CSH) media by Clostridium acetobutylicum CICC 8016. CaCO3 addition stimulated sugars utilization and butanol production. Further study showed that calcium salts addition to CSH media led to the increase in Ca2+ concentration both intracellularly and extracellularly. Interestingly, without calcium salts addition, intracellular Ca2+ concentration in the synthetic P2 medium was much higher than that in the CSH medium despite the lower extracellular Ca2+ concentrations in the P2 medium. These results indicated that without additional calcium salts, Ca2+ uptake by C. acetobutylicum CICC 8016 in the CSH medium may be inhibited by non-sugar biomass degradation compounds, such as furans, phenolics and organic acids. Comparative proteomics analysis results showed that most enzymes involved in glycolysis, redox balance and amino acids metabolism were up-regulated with CaCO3 addition. This study provides further insights into the role of CaCO3 in n-butanol production using real biomass hydrolysate

Glycerol-assisted one-step instant catapult steam explosion enhances enzymatic digestibility of corn stover

Glycerol-assisted one-step instant catapult steam explosion (ICSE) was studied for corn stover pretreatment. Glycerol addition reduced lignin content from ∼32 % to ∼24 % in pretreated solid residues with a stover/glycerol ratio from 1:0.0 to 1:2.0. Glycerol addition might help to reduce the formation of pseudo-lignin with the reduction of the total lignin recovered in pretreated solid residue from 114 % (possibly because of pseudo-lignin contribution) to 81 %. Furthermore, atomic forced microscopy analysis showed that glycerol addition improved surface roughness of pretreated corn stover. Moreover, it was proposed that glycerol-assisted ICSE likely led to the reactions of glycerol with lignin and lignin-derivatives through α-etherification and γ-esterification, preserving lignin internal β-O-4 linkages and preventing lignin condensation. Finally, enzymatic hydrolysis of corn stover pretreated by glycerol-assisted ICSE at a stover/glycerol ratio of 1:1 led to a glucan digestibility in solid residues of 98.4 % and a glucose yield of 79.3 %, which were 27.9 % and 44.7 % higher than those without glycerol addition, respectively.</p

Ultrafast excited state intramolecular proton/charge transfers in novel NIR-emitting molecules

The unusual large bathochromic shift from a novel near-infrared (NIR)-emitting molecule, 2-[3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylstyr-yl]-3-ehtylbenzo[d]thiazol-3-ium iodide (named cyanine 1) with combination of intramolecular charge transfer (ICT) and intramolecular proton transfer (IPT) process in one molecular framework, is systematically investigated using ultrafast transient absorption (TA) spectroscopy and quantum chemical calculations. In order to understand the synergetic coupling effect of the excited state intramolecular proton/charge transfers (ESIPT/ESICT) for the intense near-infrared emission of cyanine 1, an analogue non-ESIPT molecule, 2-[5-(benzo[d]thiazol-2-yl)-2-hydroxystyryl]-3-ehtylbenzo[d]thiazol-3-ium iodide (named cyanine 2) has also been investigated as comparison. Steady-state spectra and theoretical calculations suggest that the large Stokes shift and high fluorescence quantum yield in cyanine 1 originate from the ultrafast ESIPT, which leads to the efficient extension of π-conjugation in the molecular backbone in its excited states. Femtosecond transient absorption spectra further confirm above-mentioned conclusion that an extremely fast ESIPT process occurs in cyanine 1 upon excitation, followed by a solvent reorganization process (ca. 1.5 ps). This solvation is obviously slower compared to cyanine 2 (ca. 0.8 ps), indicating the extent of ESICT concerned ESIPT in keto* form of cyanine 1 is slightly weaker than that of ESICT in cyanine 2, where the fast ESIPT plays an important role in extending the efficient π-conjugation in the molecular backbone by adjusting the electronic charge distribution in keto* form. Such an effect can reduce the radiationless transition due to weak solvation process in keto* form, and then promotes the quantum yield of the large red-shifted fluorescence in cyanine 1

Tailored production of citric acid and mannitol by Yarrowia lipolytica from corn stover pretreated by glycerol-assisted instant catapult steam explosion

Yarrowia lipolytica CGMCC 2.1506 was studied for tailored production of citric acid and mannitol by co-utilization of glucose and glycerol as carbon sources. Firstly, optimal cultivation conditions for producing the two products were determined using synthetic (SYN) media. The determined conditions were further applied and verified by Y. lipolytica cultivated with corn stover enzymatic hydrolysate (CSH) media derived from glycerol-assisted instant catapult steam explosion (ICSE) without detoxification, glycerol removal or nutrient addition. A high citric acid concentration of 63.8 ± 2.6 g/L was achieved from CSH media containing 50.0 ± 0.8 g/L glucose and 46.3 ± 2.3 g/L glycerol, in a 5 L bioreactor at pH 5.5. In contrast, a high mannitol concentration of 37.1 ± 1.5 g/L was obtained from a similar hydrolysate at pH 3.5. This study demonstrated that the integrated process based on glycerol-assisted ICSE pretreatment and tailored production of two important building block chemicals by Y. lipolytica is promising for biorefining of lignocellulosic biomass.</p