X-ray crystallography provides the vast majority of macromolecular structures, but the success of the method relies on growing crystals of sufficient size. In conventional measurements, the necessary increase in X-ray dose to record data from crystals that are too small leads to extensive damage before a diffraction signal can be recorded1-3. It is particularly challenging to obtain large, well-diffracting crystals of membrane proteins, for which fewer than 300 unique structures have been determined despite their importance in all living cells. Here we present a method for structure determination where single-crystal X-ray diffraction ‘snapshots’ are collected from a fully hydrated stream of nanocrystals using femtosecond pulses from a hard-X-ray free-electron laser, the Linac Coherent Light Source4. We prove this concept with nanocrystals of photosystem I, one of the largest membrane protein complexes5. More than 3,000,000 diffraction patterns were collected in this study, and a three-dimensional data set was assembled from individual photosystem I nanocrystals (~200 nm to 2 μm in size). We mitigate the problem of radiation damage in crystallography by using pulses briefer than the timescale of most damage processes6. This offers a new approach to structure determination of macromolecules that do not yield crystals of sufficient size for studies using conventional radiation sources or are particularly sensitive to radiation damage.

Intestinal luminal microbiota likely contribute to the etiology of necrotizing enterocolitis (NEC), a common disease in preterm infants. Microbiota development, a cascade of initial colonization events leading to the establishment of a diverse commensal microbiota, can now be studied in preterm infants using powerful molecular tools. Starting with the first stool and continuing until discharge, weekly stool specimens were collected prospectively from infants with gestational ages ≤32 completed weeks or birth weights≤1250 g. High throughput 16S rRNA sequencing was used to compare the diversity of microbiota and the prevalence of specific bacterial signatures in nine NEC infants and in nine matched controls. After removal of short and low quality reads we retained a total of 110,021 sequences. Microbiota composition differed in the matched samples collected 1 week but not <72 hours prior to NEC diagnosis. We detected a bloom (34% increase) of Proteobacteria and a decrease (32%) in Firmicutes in NEC cases between the 1 week and <72 hour samples. No significant change was identified in the controls. At both time points, molecular signatures were identified that were increased in NEC cases. One of the bacterial signatures detected more frequently in NEC cases (p<0.01) matched closest to γ-Proteobacteria. Although this sequence grouped to the well-studied Enterobacteriaceae family, it did not match any sequence in Genbank by more than 97%. Our observations suggest that abnormal patterns of microbiota and potentially a novel pathogen contribute to the etiology of NEC.

Reactive oxygen species (ROS) scavenging Mn3O4 nanozymes effectively protected live mice from ROS-induced ear-inflammation in vivo.

Nanozymes are nanomaterials with enzyme-like characteristics, which have found broad applications in various areas including bionanotechnology and beyond.

2019-nCov has caused more than 80 deaths as of 27 January 2020 in China, and infection cases have been reported in more than 10 countries. However, there is no approved drug to treat the disease. 2019-nCov M pro is a potential drug target to combat the virus. We built homology models based on SARS M pro structures, and docked 1903 small molecule drugs to the models. Based on the docking score and the 3D similarity of the binding mode to the known M pro ligands, 4 drugs were selected for binding free energy calculations. Both MM/GBSA and SIE methods voted for nelfinavir, with the binding free energy of -24.69±0.52 kcal/mol and -9.42±0.04 kcal/mol, respectively. Therefore, we suggested that nelfinavir might be a potential inhibitor against 2019-nCov M pro .author/funder. All rights reserved. No reuse allowed without permission.

This longitudinal study on 94 families examined the extent to which parent sensitivity, infant affect, and affect regulation at 4 months predicted mother-infant and father-infant attachment classifications at 1 year. Parent sensitivity was rated from face-to-face interaction episodes; infant affect and regulatory behaviors were rated from mother-infant and father-infant still-face episodes at 4 months. Infants' attachment to mothers and fathers was rated from the Strange Situation at 12 and 13 months. MANOVAs indicated that 4-month parent and infant factors were associated with infant-mother but not infant-father attachment groups. Discriminant Function Analysis further indicated that two functions, "Affect Regulation" and "Maternal Sensitivity," discriminated infant-mother attachment groups; As and B1-B2s showed more affect regulation toward mothers and fathers than B3-B4s and Cs at 4 months, and mothers of both secure groups were more sensitive than mothers of Cs. Finally, the association between maternal sensitivity and infant-mother attachment was partially mediated by infant affect regulation.

lithography process, using the increase in the T g of the photoresist particles caused by UV-induced crosslinking. Subsequent deposition of silica through the patterned-colloidal mask yielded ordered domains of nanoscale-hole arrays on a micrometer length scale. The present technique produces a spatially organized mask with multiple length scales for colloidal lithography. As such, various functional materials can be deposited through these multiscale colloidal masks, fabricating nanopatterned substrates, which are of practical significance in a wide range of applications from biosensors to optoelectronic devices. ExperimentalSynthesis of Photoresist Particles: MMA (Aldrich, > 99 %) and GMA (Aldrich, > 95 %) were used as supplied. Potassium persulfate (KPS) was used as an initiator for emulsion polymerization. A 100 mL two-necked round-bottom flask was filled with KPS dissolved in 50 mL of distilled water, and a monomer mixture of MMA and GMA. The content of KPS was fixed at 1 wt.-%. The content of GMA was varied in the range 5-30 wt.-% of the total monomer content, which was fixed at 10 wt.-%. The system was kept under a nitrogen atmosphere and the reaction mixture was stirred magnetically at 300 rpm. When the KPS was dissolved completely, the mixture was heated to 75°C using an oil bath. After 12 h, the mixture was separated by centrifugation and was purified with distilled water several times. The size of the particles, measured by SEM, ranged from 360 to 420 nm. Later, the cationic photoinitiator, Irgacure 250, was introduced to the photoresist particles by spin-coating.Measurement of T g : The glass-transition temperatures of the UV-exposed and UV-screened poly(MMA-co-GMA) particles were determined using a differential scanning calorimeter (DSC, TA Instruments, Q1000) under a nitrogen atmosphere at a heating rate of 10°C min -1 . To measure the T g of UV-exposed particles, the particles were fully baked at 150°C for 2 h after UV exposure, because the crosslinking reaction could proceed during the DSC measurement. Therefore, the measured T g could be higher than the T g of the UV-exposed particles in the patterning. Meanwhile, T g of the UV-screened particles was compared with that estimated using the rule-of-mixtures theory where T g = 115°C for polyMMA and T g = 75°C for polyGMA [19].Deposition of Silica: Silica was deposited in a batch reactor under atmospheric pressure at room temperature. The sample was sequentially exposed to water vapor for 30 min, dried in argon gas for purging the reactor, and then SiCl 4 vapor for 20 min. The reactant vapors were carried by argon gas under atmospheric pressure. The concentration of SiCl 4 was 0.05 vol.-% in moisture-free argon gas and the relative humidity of water vapor was 50 %. (Caution: silicon tetrachloride is a very corrosive liquid. Use it only with adequate ventilation, and wear protective clothing and safety goggles.) The thickness of the silica layer was controlled by the exposure time to the precursor vapor and around 50 nm for 30 min exposure was obtained.

X-ray free-electron lasers have enabled new approaches to the structural determination of protein crystals that are too small or radiation-sensitive for conventional analysis1. For sufficiently short pulses, diffraction is collected before significant changes occur to the sample, and it has been predicted that pulses as short as 10 fs may be required to acquire atomic-resolution structural information1–4. Here, we describe a mechanism unique to ultrafast, ultra-intense X-ray experiments that allows structural information to be collected from crystalline samples using high radiation doses without the requirement for the pulse to terminate before the onset of sample damage. Instead, the diffracted X-rays are gated by a rapid loss of crystalline periodicity, producing apparent pulse lengths significantly shorter than the duration of the incident pulse. The shortest apparent pulse lengths occur at the highest resolution, and our measurements indicate that current X-ray free-electron laser technology5 should enable structural determination from submicrometre protein crystals with atomic resolution.