Free-standing polymer-metal-organic framework membrane with high proton conductivity and water stability

As a new class of porous material,polymer-metal-organic framework(polyMOF)has attracted tremendous interests owing to their combined advantages of polymer and crystalline MOF.However,the poor film-forming ability of polyMOF limits its widespread application,especially in membrane separation area.Herein,for the first time,we demonstrate the fabrication of freestanding polyMOF membrane.The polyMOF nanosheets are synthesized by a polymer-assisted self-inhibition crystal growth strategy.Followed by self-assembly through vacuum filtration,a 20μm-thick free-standing polyMOF membrane is constructed.Benefiting from the inclusion of polymer with hydrophobic backbone and the continuously distributed non-coordinated hydrophilic groups along polymer chain,the polyMOF membrane attains excellent structure stability against water,as well as superior proton transfer property.Proton conductivity as high as 112 and 25.6 mS·cm^(–1)is obtained by this polyMOF membrane at 100%and 20%relative humidity(RH),respectively,which are two orders of magnitude higher than those of pristine MOF.The conductivity under low humidity(20%RH)is even over 8 times higher than that of commercial Nafion membrane(3 mS·cm^(–1)).This study may provide some guidance on the development of polyMOF membranes.

Functional response of the fungus Hirsutella rhossiliensis to the nematode, Heterodera glycines

Functional response is a key index in determining the population fluctuation in predation. However, the lack of operable research system limits the studies on functional response of fungal predators. Hirsutella rhossiliensis is a dominant parasite of the soybean cyst nematode, Heterodera glycines. In a soil microcosm bioassay, we determined fungal biomass at different days within 21 days after inoculation, and parasitism rate of H. glycines by the fungus was determined. The functional response of H. rhossiliensis to H. glycines was established and found to be Holling＇s type Ill, which was influenced by mycelial densities. Meanwhile, we conducted anti-fungal analysis of metabolic fractions extracted from H. rhossiliensis to explain the potential mechanism of the intraspecific competition illustrated by functional response. The result of anti-fungal experiments indicated that the fungal predators had more complicated interaction at population level than expected, which might be regulated by self-inhibition metabolite（s）. This study was the first functional response study of fungal predators in microcosm. With the in- creasing recognition of emerging fungal threats to animal, plant, and ecosystem health, the methodologies and hypotheses proposed in this study might inspire further research in fungal ecology.

The structure of 4-hydroxylphenylpyruvate dioxygenase complexed with 4-hydroxylphenylpyruvic acid reveals an unexpected inhibition mechanism

4-Hydroxyphenylpyruvate dioxygenase(HPPD)is an important target for both drug and pesticide discovery.As a typical Fe(II)-dependent dioxygenase,HPPD catalyzes the complicated transformation of 4-hydroxyphenylpyruvic acid(HPPA)to homogentisic acid(HGA).The binding mode of HPPA in the catalytic pocket of HPPD is a focus of research interests.Recently,we reported the crystal structure of Arabidopsis thaliana HPPD(At HPPD)complexed with HPPA and a cobalt ion,which was supposed to mimic the pre-reactive structure of At HPPD-HPPA-Fe(II).Unexpectedly,the present study shows that the restored At HPPD-HPPA-Fe(II)complex is still nonreactive toward the bound dioxygen.QM/MM and QM calculations reveal that the HPPA resists the electrophilic attacking of the bound dioxygen by the trim of its phenyl ring,and the residue Phe381 plays a key role in orienting the phenyl ring.Kinetic study on the F381 A mutant reveals that the HPPD-HPPA complex observed in the crystal structure should be an intermediate of the substrate transportation instead of the pre-reactive complex.More importantly,the binding mode of the HPPA in this complex is shared with several well-known HPPD inhibitors,suggesting that these inhibitors resist the association of dioxygen(and exert their inhibitory roles)in the same way as the HPPA.The present study provides insights into the inhibition mechanism of HPPD inhibitors.