Conversion of Natural Forest to Rubber Plantation Decreases Methane Sink Strength (Agriculture)

The loss of soil carbon is mainly through emission of carbon, in the forms of carbon dioxide (CO2) and methane (CH4) as greenhouse gases (GHG), from the soil into the atmosphere. Measuring CO2 and CH4 emissions from rubber plantations provides estimates of carbon loss potential due to shifts in soil conditions and plant types as the lands changed from primary tropical forests. 

Many studies have compared GHG emissions from rubber plantation soils to those from primary forest soils over a short term (less than 3 years). However, studies after more than10 years of land conversion are rare. 

In a study published in Agricultural and Forest Meteorology, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) measured CO2 and CH4 fluxes from a rubber plantation which has been actively managed for over 10 years and from a local primary tropical rainforest in Xishuangbanna. They also compared the fluxes from these two sites. 

They found that the conversion of tropical rainforest to rubber plantation did not change CO2 emissions very much, but decreased the sink strength for CH4 significantly. 

The researchers then tried to explore the factors that control CO2 and CHfluxes different between the two sites. 

The soil CHfluxin the tropical rainforest is affected by a combination of soil temperature, soil dissolved nitrogen, microbial biomass nitrogen, nitrate–nitrogen, dissolved organic nitrogen, and decomposed fine roots. Among the factors, soil temperature was the most important control. By contrast, the most important control in the rubber plantation was water content. 

“Our results suggest that the soil biogeochemical processes associated with fine roots and C and N mineralization should be considered as effects of land use change on soil C dynamics and emissions,” said Prof. ZHANG Yiping of XTBG.

Featured image: Graphical abstract by Zhang et al.


Reference

Drivers of difference in CO2 and CH4 emissions between rubber plantation and tropical rainforest soils


Provided by Chinese Academy of Sciences

Researchers Improve Plant Prime Editing Efficiency with Optimized pegRNA Designs (Botany)

Precision genome editing enables the precise modification of DNA in living cells, thus enabling a breadth of opportunities for plant breeding. Prime editors, developed by Prof. David R. Liu and his colleagues, permit the installation of desired edits in a programmable target site. They are comprised of an engineered Cas9 nickase (H840A)-reverse transcriptase (RT) fusion protein and a prime editing guide RNA (pegRNA).

Prime editors were previously developed and optimized as an extremely versatile editing strategy for generating programmable point mutations, insertions and deletions in rice and wheat by Prof. GAO Caixia of the Institute of Genetics and Developmental Biology (IGDB) of the Chinese Academy of Sciences along with her research team and collaborators.

They found that the editing efficiency of the plant prime editor was strongly affected by the PBS and RT template sequence, suggesting the need for optimized pegRNA designs to yield higher product conversions.

To determine principles for efficient prime editing, Prof. GAO and Prof. LI Jiayang, also of IGDB, along with their research teams, reported optimized pegRNA design strategies that maximize plant prime editing efficiency.

Since the hybridization of the primer binding site (PBS) with the non-target strand ssDNA is the initial step in reverse transcription, the researchers hypothesized that the melting temperature (Tm) of the PBS sequence (referred to hereafter as PBS Tm) is an important parameter for prime editors. By analyzing prime editing efficiencies at 18 endogenous target sites in rice protoplasts, they found that PBS Tm strongly affects editing efficiency, with maximal prime editing occurring when PBS Tm is 30 °C in rice.

In addition to identifying optimal pegRNA designs, they also introduced advances to prime editing through the use of dual pegRNAs. This strategy relies on two pegRNAs generating respective ssDNA flaps that base pair with each other in trans while encoding the same edit on both strands of the newly synthesized DNA.

This new editing approach resulted in 3.0-fold improvements in average in prime editing efficiency compared to using individual pegRNAs alone. Furthermore, the scientists generated prime editors comprised of SpG (an engineered Cas9 with expanded PAM targeting range) to expand the targeting scope of this dual-pegRNA editing strategy. Together, optimizing PBS Tm and using a dual-pegRNA strategy boosted prime editing efficiency up to 17.4-fold in rice.

Based on these two advancements, the team developed a user-friendly web application, PlantPegDesigner, to help other researchers design prime editing tools best suited for their applications.PlantPegDesigner offers users flexibility and control of various parameters based on their individual needs.

This tool recommends spacer-PAM sequences, PBS sequences, RT template sequences and also PCR cloning primers for vector construction. Compared to other web applications, PlantPegDesigner-recommended dual pegRNAs resulted in up to a 46-fold improvement in editing activity in rice. 

In summary, this work simplified the design of pegRNAs, thus providing a reliable solution for efficient prime editing in plants. The flexibility of the optimized plant prime editing system will advance both plant breeding and functional genomics research.

This study, entitled “High-efficiency prime editing with optimized, paired pegRNAs in plants,” was published in Nature Biotechnology online on March 25.

This research was supported by the National Transgenic Science and Technology Program of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, and the National Natural Science Foundation of China.

Featured image: The optimized plant pegRNA design for prime editing (Image by IGDB). (a) Diagram of optimizing the PBS Tm. (b) Prime editing frequencies at different PBS Tm in rice. (c) Diagram of prime editing using the dual-pegRNA strategy. (d) Comparison of the dual-pegRNA strategy with either pegRNA alone. (e) Schematic representation of using PlantPegDesigner to design pegRNAs. (Image by IGDB)


Reference

High-efficiency prime editing with optimized, paired pegRNAs in plants


Provided by Chinese Academy of Sciences

Research Reveals Mechanism of Salinity Tolerance in Italian Ryegrass (Botany)

Italian ryegrass (Lolium multiflorum) is a widely cultivated forage with excellent quality, high yield, good palatability and rich nutritional value. However, its growth is inhibited by salt tress, which is a major growth limiting factor.  

In order to elucidate the salt tolerance mechanism of two Italian ryegrass cultivars, FENG Qijia, co-advised by Prof. CHEN Liang and assistant Prof. XIE Yan from the Wuhan Botanical Garden of the Chinese Academy of Sciences (CAS) investigated the possible salinity tolerance mechanisms between the salt-tolerant/-sensitive Italian ryegrass cultivars, ‘Abundant’ and ‘Angus’, via the physiological traits and the metabolomics. 

Salt stress decreased the shoot growth rate and relative water content in both cultivars, to a larger extent in the salt-sensitive ‘Angus’ than salt-tolerant ‘Abundant’ cultivar. The photosynthetic efficiency responses to salt stress confirmed that the ‘Abundant’ cultivar exhibited better salt tolerance than ‘Angus’. The Na/K, Na/Mg and Na/Ca ratios in the leaves and roots increased significantly in both cultivars under salt treatment, with higher ratios in salt-sensitive ‘Angus’ than in salt-tolerant ‘Abundant’.  

The first line of defense is the absorption of Na by roots and the ability to transport it upward. Salt-tolerant ‘Abundant’ absorbed less, thus reducing osmotic and toxic effects. When exposed to salt conditions, the salt-sensitive ‘Angus’ had higher level of metabolites and more uniquely up-regulated metabolites, which may confer ‘Abundant’ to a better growth than ‘Angus’.    

The ‘Abundant’ cultivar has got better growth than ‘Angus’ cultivar, and its high tolerance of salt partly prevents the plant from ionic homeostasis disruption. 

The results have been published in Physiologia Plantarum entitled “Comparative physiological and metabolic analyses of two Italian ryegrass (Lolium multiflorum) cultivars with contrasting salinity tolerance“. 

This work was supported by the grants from the Youth Innovation Promotion Association of CAS, the National Natural Science Foundation of China, the Changsha Municipal Science and Technology Project, and the Major Science and Technology Innovation Project of Shandong Province.

Featured image: Speculated model for Italian ryegras grown with 300 mM salt stress. (Image by FENG Qijia)


Reference

Comparative physiological and metabolic analyses of two Italian ryegrass (Lolium multiflorum) cultivars with contrasting salinity tolerance


Provided by Chinese Academy of Sciences

Scientists Reveal How Dopamine and Its Activity Regulator Bind to Dopamine Receptor D1 (Neuroscience)

In a study published in Cell Research, Prof. H. Eric Xu from Shanghai Institute of Materia Medica of the Chinese Academy of Sciences, collaborating with Prof. Bryan Roth from University of North Carolina Chapel Hill, Prof. ZHANG Yan from Zhejiang University, and the collaborators, reported the near-atomic structure of dopamine (DA) receptor D1 bound with DA, and revealed the high-resolution structure of D1R with its positive allosteric modulator LY3154207. 

DA is an important monoamine neurotransmitter involved in the regulation of various physiological functions of the central nervous system (CNS) and the peripheral nervous system (PNS). It conducts signal transformation through five DA receptors (DRs), namely, D1R, D2R, D3R, D4R and D5R. All the DRs belong to the G protein-coupled receptor (GPCR) superfamily.

Among DRs, D1R is most abundantly expressed in CNS. Dysfunction of D1R is associated with various neurological diseases such as Parkinson’s disease, schizophrenia, and drug addiction, making it an important drug target for developing efficient treatments of neuropsychiatric diseases. 

For a long time, as the endogenous ligand of D1R, the detail of how DA recognizes and activates D1R was poorly investigated. The cellular activities of D1R agonists, such as DA, can be regulated by D1R positive allosteric modulators (PAMs). However, the mechanisms remain unknown of how PAMs regulate D1R conformation and promote the cellular activity of D1R agonists.

To answer these questions, scientists determined the structures of D1R PAM LY3154207 bound D1R-Gs signaling complexes activated by either DA or a synthetic agonist SKF81297. They found that the overall interaction patterns of DA and SKF81297 with D1R are similar. The noticeable difference is that DA lacks an extended binding pocket (EBP) that interacts with D1R, which makes its affinity to D1R weaker than SKF81297. 

The structures clearly showed the binding pose of PAM LY3154207. LY3154207 molecule lies in the cleft between TM3 and TM4 and right above ICL2 with a boat conformation. Interestingly, the binding pose of LY3154207 in this study is different from that obtained by molecular dynamics simulation in previous studies, and the binding mode of LY3154207 in this study is also divergent from the recently reported structure of D1R binding to LY3154207.

By comparing the structures of D1R-SKF81297 in the presence or absence of LY3154207, scientists found that LY3154207 may help keeping D1R in its active state, thereby enhancing the activation efficiency of agonists.

“In this study, we present the clear view of human D1R bound to its endogenous agonist DA and allosteric modulator LY3154207 compound. The series of D1R structures, as we published in Cell last month, present a more complete landscape in understanding pharmacology of D1R, and provide multiple templates in designing more efficient and safer drugs treating CNS diseases,” one of the corresponding authors, Prof. H Eric. Xu said.

Featured image: Structures of DA or SKF81297 bound D1R-Gs complexes, both in presence of PAM. (Image by H. Eric Xu’s group)


Reference

Mechanism of dopamine binding and allosteric modulation of the human D1 dopamine receptor


Provided by Chinese Academy of Sciences

Edible Yellow Chanterelles Commonly Sold in Mushroom Markets of Yunnan Are Cantharellus Yunnanensis (Food)

Cantharellus cibarius is the type species of the fungi genus Cantharellus. Together with some other yellow chanterelles, Cantharellus cibarius has been recorded among the edible mushrooms sold in markets in China and is commonly referred to as Ji-You-Jun, meaning chicken fat, due to its yellow color. However, there’s no morphological description or evidence available for the identified species. 

“It becomes very important to confirm the species identity and carry out taxonomic re-evaluation of this fungi genus by using integrated taxonomic approaches,” said Dr. SHAO Shicheng from the Xishuangbanna Tropical Botanical Garden (XTBG). 

Researchers at XTBG and their collaborators collected yellow chanterelles from various sites and markets in Guizhou, Jilin and Yunnan Provinces from 2007 to 2019 for morphological and molecular analysis. By using the maximum likelihood and Bayesian inference methods, they amplified the transcription elongation factor 1-alpha (tef-1α) gene with the primers tef1F and tef1R and analyzed the tef-1α sequences.

Cantharellus yunnanensis (Image by SHAO Shicheng)

Morphological and molecular analysis confirmed that the edible yellow chanterelles commonly sold in the mushroom markets of Yunnan Province are not Ccibarius, but Cyunnanensis instead. The epithet “yunnanensis” refers to the distribution of these species in different areas of Yunnan Province, China. 

Moreover, the researchers presented a new and accurate record of C. cibarius from the northeastern part in China based on morphological and molecular evidence. They thus confirmed that the distribution of Ccibarius is not restricted to northern Europe and America. The occurrence of C. cibarius in China is limited to Northern China.

Edible yellow chanterelles commonly sold in mushroom markets of Yunnan (Image by WANG Xianghu)

Since Ccibarius and Cyunnanensis are very similar morphologically, it’s difficult to identify them. The researchers proposed the general coloration as a key feature for identifying and delimiting both species: C. cibarius displays an orange-yellow to bright yel-low color and a plane pileus, while Cyunnanensis displays paler basidiomata and a convex pileus. 

The study entitled “New insights into the taxonomy of the genus Cantharellus in China: epityfication of C. yunnanensis W.F. Chiu and the first record of C. cibarius Fr.” has been published in Cryptogamie Mycologie.

Featured image: Cantharellus cibarius (Image by WANG Xianghu)


Reference

New insights into the taxonomy of the genus Cantharellus in China: epityfication of C. yunnanensis W.F. Chiu and the first record of C. cibarius Fr


Provided by Chinese Academy of Sciences

New Study Finds Strong Immune Response Following COVID-19 Vaccination (Medicine)

A new study carried out in collaboration with the University of Birmingham with support from the UK Coronavirus Immunology Consortium has found that 99% of people generate a robust immune response against COVID-19 after just one dose of the Pfizer vaccine.

The Protective Immunity from T cells to COVID-19 in Health workers study (PITCH) examined how the immune system responds to COVID-19 after one dose of the Pfizer vaccine among people who have been infected by COVID-19 before and those who have not.

It suggests one dose of the vaccine protects against severe disease, supporting the decision to delay the second dose and provide protection to as many higher-risk groups as possible by providing more first doses. The study showed after two doses levels of protection were even stronger, underlining the importance of people coming forward for their second dose.

Between December 2020 and February 2021, researchers from the Universities of Sheffield, Oxford, Birmingham, Liverpool, and Newcastle, analysed blood samples from 237 healthcare workers to understand their T cell and antibody responses following vaccination from the Pfizer vaccine.

The study also sheds light on the impact of previous infection from COVID-19 on people’s immune response to vaccination. It found people who had previously been infected with COVID-19 showed higher T cell and antibody responses after one dose of the Pfizer vaccine compared with people who had never had COVID-19 before and had one dose of the vaccine.

The researchers discovered that among people who had had COVID-19 in the past, the T cell response expanded after vaccination to recognise more regions of the COVID-19 spike protein – which attacks the immune system and causes severe disease. This means, even in those already infected, vaccination from the Pfizer jab provides better protection and an enhanced immune response to COVID-19 than the immune response from natural infection, further supporting the need for a vaccination programme.

It is not yet known how long T cell and antibody response lasts following infection. The first dose of both the Pfizer and AstraZeneca vaccine offer good levels of protection, but to get maximum protection it is vital everyone gets a second dose when invited as two doses of the vaccine will provide longer-lasting protection from the virus.

Professor Paul MossUK Coronavirus Immunology Consortium lead from University of Birmingham, said: “Vaccines are a crucial part of our roadmap out of this pandemic. To maximise their impact, it’s critical that we understand the underlying biology of how they induce immunity in different groups of people.

“When working in a pandemic, time is of the essence. This collaborative approach to science, working with multiple partners at scale, is allowing us to drive forward our knowledge at an unprecedented rate.

“The UK Coronavirus Immunology Consortium, working with PITCH, is a great example of how this team science approach can answer these key questions and help us hasten effective pandemic control.”

Health and Social Care Secretary Matt Hancock said: “The PITCH study presents further proof that vaccines provide excellent protection against the virus. Thanks to the incredible efforts of our vaccination programme, over half of all adults in the UK have had the jab, and we remain on track to offer all adults a vaccine by the end of July.

“The vaccine has already saved thousands of lives in the UK. A second vaccine jab is crucial for longer-term protection, regardless of whether you have previously had COVID-19 or not, and I urge everyone to make sure they attend their second appointment – to keep themselves and those around them safe.”

Health Minister Lord Bethell said: “These findings from the PITCH study are crucial to increasing our understanding of the immune response to COVID-19 and how the Pfizer vaccine is working to protect people across the UK already.

“I urge everyone to come forward to be vaccinated when invited and to take up both doses of the vaccine as both are vital to ensuring long term protection from COVID-19.”

Key findings from the PITCH study:

  • Among individuals who had not had COVID-19 in the past and had received two doses of the Pfizer vaccine, T cell response was as strong as people who had had previous COVID-19 infection and one vaccine dose;
  • After one dose of the Pfizer vaccine, individuals who had previous COVID-19 infection showed higher antibody and T cell responses compared with people who had not been infected before. Antibody responses were 6.8 times higher and T cell responses 5.9 times higher;
  • Among individuals who had not had COVID-19 in the past and had received one dose of the Pfizer vaccine, antibody and T cell responses were at a similar or higher level compared to those who had previously been infected but not been vaccinated;
  • There was no link between age and levels of T cell/antibody response

An effective vaccine is one that that saves lives and reduces hospitalisations. Both the Pfizer and Oxford-AstraZeneca vaccines have been shown to be highly effective in reducing COVID-19 infections among older people aged 70 years, according to previously published research carried out by Public Health England. In the over 80s, data suggest that a single dose of either vaccine is more than 80% effective at preventing hospitalisation, around 3 to 4 weeks after the jab.

Further research will continue to deepen our understanding of the immune responses over the longer term and what it means for protection against COVID-19 in the real world.

Dr Thushan de Silva, study author from the University of Sheffield, said: “Our study is one of the largest and most comprehensive accounts of the immune response to one dose of Pfizer/BioNTech vaccine comparing previously infected and infection-naive individuals.

“Our results demonstrate that T cell and antibody responses induced by natural infection are boosted significantly by a single dose of vaccine.

“While the response to a single dose was lower in infection-naïve individuals, it was still equivalent or better than the immunity in previously infected individuals before it is boosted by vaccination.”

Professor Susanna Dunachie, PITCH study lead from the University of Oxford, said: “Our study highlights the importance of studying both aspects of immune protection when trying to understand the underlying mechanisms of the immune response to COVID-19 vaccination.

“Interestingly, we also found that vaccination improves the breadth of T cell responses generated in previously infected individuals.

“In immunology, this is a good thing as it means that you are more likely to maintain protection against new mutations of the virus, and further work will assess how long these vaccine responses last.

“It’s still important that everyone follows NHS guidelines to get two doses of the vaccine, even if you think you may have previously had COVID-19.

“The PITCH Study has been a great opportunity to work collaboratively across five university hospitals and with Public Health England to look at T cell responses to SARS-CoV-2 at greater scale and depth than a single research centre can.

“By building on the national SIREN Study and putting our heads together, we are contributing towards illuminating the role of T cells in protection against COVID-19 from vaccines and previous infection.”

Professor Paul Klenerman, PITCH study lead from the University of Oxford, said: “T cells are an important component of immunity to viruses – but typically much harder to measure than antibodies.

“To set this up at scale across the UK in the midst of a pandemic was a big challenge but the very clear data found by PITCH show just how informative this approach can be.”


Reference: Angyal et al (March, 2021). ‘T-cell and antibody responses to first BNT162b2 vaccine dose in previously SARS-CoV-2-infected and infection-naive UK healthcare workers: a multicentre, prospective, observational cohort study.’ 


Provided by University of Birmingham

Novel Cathode Designed for High-performance Sodium Ion Batteries (Material Science)

Due to their large-scale energy storage, sodium ion batteries (SIBs) are a promising alternative to lithium-ion batteries (LIBs). However, it’s challenging to develop high-energy and high-power SIBs due to the greater atomic mass and larger ionic radius.

Electrode architecture design with high mass loading of active materials is a more straightforward strategy to achieve high energy. It can increase the percentage of active materials and consequently energy density at device/cell levels.

Recently, a research group led by Prof. LI Xianfeng and Dr. ZHENG Qiong from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) designed and optimized a low-tortuosity and high-areal-capacity cathode for high-rate and ultra-stable SIBs.

The results were published in Advanced Energy Materials on March 18. 

The researchers proposed a low-tortuosity, finger-like composite electrode with ultra-high mass loading based on nonsolvent-induced phase separation method, which could offer well-pleasing electron/ion transport pathway and relatively low battery resistance.

Benefiting from the structural advantages, they obtained the as-prepared electrode with ultra-high mass loading (60 mg/cm2) and areal capacity (4.0 mAh/cm2). Even at a high rate of 10 C, the areal capacity remained 1.0 mAh/cm2.

The researchers also illustrated the homogeneous Na+ distribution, gentle and uniform local current density and polarization inside the as-prepared electrode.

Combining numerical simulations and experiments, they revealed that the low-tortuosity architecture could contribute to an impressive ion transport capability and consequently significant improvements in electrochemical performance.

This study exhibits a prospective solution for design and optimization of the low-tortuosity electrodes with ultra-high mass loading, which opens a new avenue for developing advanced SIBs with high energy/power density.

This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the National Natural Science Foundation of China, Youth Innovation Promotion Association of CAS, and the Dalian National Laboratory Cooperation Fund, CAS.


Reference

Controllable Design Coupled with Finite Element Analysis of Low-Tortuosity Electrode Architecture for Advanced Sodium-Ion Batteries with Ultra-High Mass Loading


Provided by Chinese Academy of Sciences

Janus Nanoreactor Designed for Bifunction of Photocatalytic Water Oxidation/reduction (Chemistry)

Janus structure is composed of two or more components with different (usually opposite) physical and chemical properties. Janus nanoparticles possess multiple surface structures that are anisotropic in shape, composition, and surface chemistry. 

Janus nanoreactors have been applied in the fields like catalysis, biomedicine, as well as energy storage and conversion. However, it remains a challenge to construct Janus nanoreactors with stable interfacial structure. 

Recently, a research team led by Prof. LIU Jian from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences, in collaboration with Prof. HU Ming from East China Normal University, reported a novel and simple strategy for the synthesis of dual-component Janus nanoreactor with asymmetric structure to realize bifunction of photocatalytic water oxidation/reduction. 

This work was published in Advanced Science on Feb. 16.

“We mimics the concepts of compartmentalization used by nature to design PBA-TiO2 Janus photocatalysts for coordinating incompatible chemical transformations,” said Prof. LIU. 

In the synthesis process, the partial dissociation of the PBA cube was induced by mild etching. The unsaturated metal sites on the PBAs could form the chemical bond with oxygen ions and Ti4+, inducing heterogeneous nucleation of TiOx on the surface of the PBA single crystals. 

Free-standing flowers assembled by TiO2 nanoflakes took root in the PBA single crystals. The PBA-TiO2 Janus nanoreactor gradually emerged and the asymmetric dual-components of nanoreactor possessed a synergistic effect due to the presence of the interfacial structure. 

The formed interfacial structure could promote the fast charge transport and effectively inhibit the photogenerated electron and hole recombination. The photocatalytic activity of PBA-TiO2 Janus nanoreactor for water oxidation/reduction was significantly higher than that of pure TiO2 and PBA catalysts. 

The above work was supported by the National Natural Science Foundation of China, and Dalian National Laboratory for Clean Energy (DNL) Cooperation Fund, Chinese Academy of Sciences. 

Featured image: A: schematic illustration of the synthetic strategy for the PBA-TiO2 Janus nanoreactor. B: TEM images of the as-prepared PBA-TiO2 Janus nanoreactors. C: comparison of photocatalytic H2 evolution and O2 evolution rate of TiO2, PBA, PBA-TiO2 Janus nanoreactors and PBA-TiO2 (mix) samples under light irradiation (Image by SHI Chunjing)  


Reference

Modular Construction of Prussian Blue Analog and TiO2 Dual-Compartment Janus Nanoreactor for Efficient Photocatalytic Water Splitting


Provided by Chinese Academy of Sciences

Researchers Develop Nanofiltration Membrane for Highly-efficient Dye/salt Separation (Chemistry)

Recently, a research group led by Prof. WAN Yinhua from the Institute of Process Engineering (IPE) of the Chinese Academy of Sciences developed a robust dually charged loose nanofiltration (NF) membrane for highly efficient dye/salt separation. 

The study was published in Journal of Membrane Science on March 21. 

NF is an effective method for treating textile wastewater. However, most commercially available NF membranes exhibit low selectivity in dye/salts separation due to their negatively charged dense separation layer.

The researchers prepared a NF membrane with a loose and dually charged separation layer based on a simple catechol-amine chemistry surface engineering strategy.  

In the strategy, polyethyleneimine (PEI) was coated on a hydrolyzed polyacrylonitrile substrate to construct a positively charged intermediate layer, followed by codeposition of tannic acid (TA) and poly-γ-glutamic acid (γ-PGA) to engineer a negatively charged top layer.  

The loose separation layer structure was attributed to the competitive reaction induced by polyphenols, which means the covalent interactions, hydrogen bonding and electrostatic adsorption among TA, γ-PGA and PEI hindered the rapid and non-uniform self-polymerization of TA. 

The pre-reaction between TA and γ-PGA could further weaken those competitive reactions, tuning the pore size and charging property, and thus improving the separation performance.  

Due to the synergy between size exclusion and electrostatic interaction of the loose dual-charged separation layer, the prepared membrane exhibited outstanding water permeability (36.9 Lm-2h-1bar-1) with low salt rejections (11.1% for Na2SO4) and high rejection to both positively and negatively charged dyes.  

Moreover, this dually charged membrane also showed excellent acid resistance as well as satisfactory antifouling performance and long-term stability.   

“This work provides a novel dimension toward the environmental-friendly approach for preparing highly selective separation membrane, and such versatile coating strategy can be employed to fabricate/modify the membrane with controllable properties for various separation applications,” said Prof. LUO Jianquan from IPE. 

Featured image: Diagram of the dually charged membrane fabricated via catechol-amine chemistry surface engineering (Image by CAO Yang)


Reference

A robust dually charged membrane prepared via catechol-amine chemistry for highly efficient dye/salt separation


Provided by Chinese Academy of Sciences