Autophagy regulates spermatid differentiation via degradation of PDLIM1

Spermiogenesis is a complex and highly ordered spermatid differentiation process that requires reorganization of cellular structures. We have previously found that Atg7 is required for acrosome biogenesis. Here, we show that autophagy regulates the round and elongating spermatids. Specifically, we found that Atg7 is required for spermatozoa flagella biogenesis and cytoplasm removal during spermiogenesis. Spermatozoa motility of atg7-null mice dropped significantly with some extra-cytoplasm retained on the mature sperm head. These defects are associated with an impairment of the cytoskeleton organization. Functional screening revealed that the negative cytoskeleton organization regulator, PDLIM1 (PDZ and LIM domain 1 [elfin]), needs to be degraded by the autophagy-lysosome-dependent pathway to facilitate the proper organization of the cytoskeleton. Our results thus provide a novel mechanism showing that autophagy regulates cytoskeleton organization mainly via degradation of PDLIM1 to facilitate the differentiation of spermatids.     

DFT investigation on the decarboxylation mechanism of <Emphasis Type="Italic">ortho</Emphasis> hydroxy benzoic acids with acid catalysis

A density functional theory (DFT) study was performed to explore the mechanisms of the acid-catalyzed decarboxylation reaction of salicylic acids using the B3LYP method with 6-31++G(d,p) basis set in both gas phase and aqueous environment. The α-protonated cation of carboxylate acid was formed during the decarboxylation process in acidic conditions, and the presence of hydrogen ions promotes decarboxylation greatly by significantly decreasing the overall reaction energy barriers to 20.98 kcal mol^?1 in gas phase and 20.93 kcal mol^?1 in water, respectively. The hydrogen in the α-carbon came directly from the acid rather than from the carboxyl group in neutral state. Compared with the reaction in gas phase, water in aqueous state causes the reaction to occur more easily. Substituents of methyl group, chlorine and fluorine at the ortho-position to the carboxyl of salicylic acid could further lower the decarboxylation energy barriers and facilitate the reaction.     

Analysis of expression and chitin‐binding activity of the wing disc cuticle protein BmWCP4 in the silkworm,Bombyx mori

The insect exoskeleton is mainly composed of chitin filaments linked by cuticle proteins. When insects molt, the cuticle of the exoskeleton is renewed by degrading the old chitin and cuticle proteins and synthesizing new ones. In this study, chitin‐binding activity of the wing disc cuticle protein BmWCP4 in Bombyx mori was studied. Sequence analysis showed that the protein had a conservative hydrophilic “R&R” chitin‐binding domain (CBD). Western blotting showed that BmWCP4 was predominately expressed in the wing disc‐containing epidermis during the late wandering and early pupal stages. The immunohistochemistry result showed that the BmWCP4 was mainly present in the wing disc tissues containing wing bud and trachea blast during day 2 of wandering stage. Recombinant full‐length BmWCP4 protein, “R&R” CBD peptide (CBD), non‐CBD peptide (BmWCP4‐CBD^?), four single site‐directed mutated peptides (M₁, M₂, M₃ and M₄) and four‐sites‐mutated peptide (M_F) were generated and purified, respectively, for in vitro chitin‐binding assay. The results indicated that both the full‐length protein and the “R&R” CBD peptide could bind with chitin, whereas the BmWCP4‐CBD^? could not bind with chitin. The single residue mutants M₁, M₂, M₃ and M₄ reduced but did not completely abolish the chitin‐binding activity, while four‐sites‐mutated protein M_F completely lost the chitin‐binding activity. These data indicate that BmWCP4 protein plays a critical role by binding to the chitin filaments in the wing during larva‐to‐pupa transformation. The conserved aromatic amino acids are critical in the interaction between chitin and the cuticle protein.     

Molecular dynamics simulations of the orientation properties of cytochrome <Emphasis Type="Italic">c</Emphasis> on the surface of single-walled carbon nanotubes

Electron transfer between cytochrome c (Cytc) and electrodes can be influenced greatly by the orientation of protein on the surface of the electrodes. In the present study, different initial orientations of Cytc on the surface of five types of single-walled carbon nanotubes (SWNTs), with different diameters and chirality, were constructed. Properties of the orientations of proteins on the surface of these tubes were first investigated through molecular dynamics simulations. It was shown that variations in SWNT diameter do not significantly affect the orientation; however, the chirality of the SWNTs is crucial to the orientation of the heme embedded in Cytc, and the orientation of the protein can consequently be influenced by the heme orientation. A new electron pathway between Cytc and SWNT, which hopefully benefits electron transfer efficiency, has also been proposed. This study promises to provide theoretical guidance for the rational design of bio-sensors or bio-fuel cells by using Cytc-decorated carbon nanotube electrodes.     

Eremophilane Sesquiterpenes from the Genus Ligularia

Ligularia speices are widely used in Asian folk medicines for the treatment of various human diseases. Eremophilane‐type sesquiterpenes are abundant and typical secondary metabolites found in this genus. Over 500 eremophilanes reported from members of Ligularia are reviewed in this article together with bioactivity data in an effort to highlight the development in this field.     

Integrated Intercalation‐Based and Interfacial Sodium Storage in Graphene‐Wrapped Porous Li4Ti5O12 Nanofibers Composite Aerogel

Sodium storage in both solid–liquid and solid–solid interfaces is expected to extend the horizon of sodium‐ion batteries, leading to a new strategy for developing high‐performance energy‐storage materials. Here, a novel composite aerogel with porous Li₄Ti₅O₁₂ (PLTO) nanofibers confined in a highly conductive 3D‐interconnected graphene framework (G‐PLTO) is designed and fabricated for Na storage. A high capacity of 195 mA h g^?1 at 0.2 C and super‐long cycle life up to 12 000 cycles are attained. Electrochemical analysis shows that the intercalation‐based and interfacial Na storage behaviors take effect simultaneously in the G‐PLTO composite aerogel. An integrated Na storage mechanism is proposed. This study ascribes the excellent performance to the unique structure, which not only offers short pathways for Na⁺ diffusion and conductive networks for electron transport, but also guarantees plenty of PLTO–electrolyte and PLTO–graphene interfacial sites for Na⁺ adsorption.     

Toward a Low‐Cost Artificial Leaf: Driving Carbon‐Based and Bifunctional Catalyst Electrodes with Solution‐Processed Perovskite Photovoltaics

Molecular hydrogen can be generated renewably by water splitting with an “artificial‐leaf device”, which essentially comprises two electrocatalyst electrodes immersed in water and powered by photovoltaics. Ideally, this device should operate efficiently and be fabricated with cost‐efficient means using earth‐abundant materials. Here, a lightweight electrocatalyst electrode, comprising large surface‐area NiCo₂O₄ nanorods that are firmly anchored onto a carbon–paper current collector via a dense network of nitrogen‐doped carbon nanotubes is presented. This electrocatalyst electrode is bifunctional in that it can efficiently operate as both anode and cathode in the same alkaline solution, as quantified by a delivered current density of 10 mA cm^?2 at an overpotential of 400 mV for each of the oxygen and hydrogen evolution reactions. By driving two such identical electrodes with a solution‐processed thin‐film perovskite photovoltaic assembly, a wired artificial‐leaf device is obtained that features a Faradaic H₂ evolution efficiency of 100%, and a solar‐to‐hydrogen conversion efficiency of 6.2%. A detailed cost analysis is presented, which implies that the material‐payback time of this device is of the order of 100 days.