Influence of Peptoid Sequence on the Mechanisms and Kinetics of 2D Assembly
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Engineering topics
Ma, Xiang
Publications and source records attributed to Ma, Xiang.
In Vivo Molecular Insights into Syntrophic Geobacter Aggregates
Direct interspecies electron transfer (DIET) has been considered as a novel and highly efficient strategy in both natural anaerobic environments and artificial microbial fuel cells. A syntrophic model consisting of Geobacter metallireducens and Geobacter sulfurreducens was studied in this work. We conducted in vivo molecular mapping of the outer surface of the syntrophic community as the interface of nutrients and energy exchange. System for Analysis at the Liquid Vacuum Interface combined with time-of-flight secondary ion mass spectrometry was employed to capture the molecular distribution of syntrophic Geobacter communities in the living and hydrated state. Principal component analysis with selected peaks revealed that syntrophic Geobacter aggregates were well differentiated from other control samples, including syntrophic planktonic cells, pure cultured planktonic cells, and single population biofilms. Our in vivo imaging indicated that a unique molecular surface was formed. Specifically, aromatic amino acids, phosphatidylethanolamine components, and large water clusters were identified as key components that favored the DIET of syntrophic Geobacter aggregates. Moreover, the molecular changes in depths of the Geobacter aggregates were captured using dynamic depth profiling. Our findings shed new light on the interface components supporting electron transfer in syntrophic communities based on in vivo molecular imaging.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Cu Interlayer-Induced High-Strength Laser-Welded AISI 304 Steel-Niobium Joint
Joining niobium to austenitic stainless steel is necessary for the fabrication of particle accelerators. However, the brittle iron-niobium intermetallics formed in the joint significantly reduce the joint strength. Copper was used as an interlayer to prevent the brittle phase formation while joining niobium to AISI 304 steel. The laser beam was first focused on the Cu-steel faying surface and then on the Cu-Nb faying surface. The tensile strength of the joint is greater than that of the Nb. The weld microstructure consists of austenite with Cu-rich precipitates along with the austenitic grain boundaries and Cu-rich phase embedded with Nb-rich particles and dendrites. Solid solution strengthening of Cu by Fe and second-phase strengthening of Cu by Nb play a critical role in improving the mechanical properties of the joint. These results highlight new possibilities for the joining of niobium to steel.
36 MATERIALS SCIENCE↗
SmpB down-regulates proton-motive force for the persister tolerance to aminoglycosides in Aeromonas veronii
Highlights: • The smpB deletion exhibited a higher susceptibility to aminoglycosides in A. veronii. • The expression level of SmpB was enhanced by gentamicin challenge. • The effect of SmpB on persistence formation was eliminated by PMF inhibition. • The smpB deletion downregulated proton-motive force-related metabolic genes. Bacterial persisters comprise a small fraction of phenotypically heterogeneous variants with transient capability for survival when exposed to high concentrations of antibiotic. In aquatic pathogenic bacteria Aeromonas veronii, Small Protein B (SmpB), the core factor of trans-translation system, was identified as a new persistence-related gene. The SmpB deletion exhibited a higher susceptibility and lower persister cell formation under aminoglycosides antibiotics pressure compared with wild type. The transcriptional and translational activities of smpB gene were significantly enhanced by the gentamicin challenge in exponential phase, but not changed in stationary phase. The transcriptomic analysis revealed that the smpB deletion stimulated the production of proton-motive force (PMF). The cell survival induced by carbonyl cyanide m-chlorophenyl hydrazone (CCCP) further verified that SmpB variation affected the quantities of PMF. Taken together, these results uncovered a novel mechanism of persister formation mediated by SmpB under aminoglycosides treatments.
60 APPLIED LIFE SCIENCES↗
MicroRNA-30c-5p inhibits NLRP3 inflammasome-mediated endothelial cell pyroptosis through FOXO3 down-regulation in atherosclerosis
Highlights: • Addition of miR-30c-5p inhibited ox-LDL-induced pyroptosis in HAECs. • NLRP3 inflammasome was associated with miR-30c-5p-mediated HEACs pyroptosis. • FOXO3 was a target of miR-30c-5p. • Silencing of FOXO3 attenuated anti-miR-30c-5p-mediated HAECs pyroptosis. Atherosclerosis is a chronic inflammatory disease involved in endothelial dysfunction. Pyroptosis is a pro-inflammatory form of cell death and plays pivotal roles in atherosclerosis. MicroRNAs (miRNAs) are implicated in atherosclerosis, however the mechanisms that underlie miR-30c-5p is required for endothelial cell pyroptosis remain elusive. In the present study, we probed the interaction of miR-30c-5p with forkhead box O3 (FOXO3) and investigated the effect of miR-30c-5p and FOXO3 on NLRP3 inflammasome and endothelial cell pyroptosis. Introduction of oxidized low density lipoprotein (ox-LDL) dose-dependently increased lactate dehydrogenase (LDH) release as well as pyroptosis in human aortic endothelial cells (HAECs). On the basis of ox-LDL treatment, we found the expression of miR-30c-5p was impaired and enrichment of miR-30c-5p protected HAECs from ox-LDL-induced pyroptosis. Moreover, addition of miR-30c-5p inhibited ox-LDL-activated NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, which was associated with HEACs pyroptosis. Nevertheless, miR-30c-5p failed to show efficacy of Toll-like receptor (TLR) signaling of NLRP3 inflammasome activation. Intriguingly, FOXO3 was suggested to be targeted by miR-30c-5p and addition of miR-30c-5p blocked FOXO3 expression, whereas miR-30c-5p depletion showed opposite effects. Furthermore, silencing of FOXO3 inhibited NLRP3-mediated pyroptosis and reversed anti-miR-30c-5p-induced activation of NLRP3 inflammasome and pyroptosis in HEACs with ox-LDL treatment. Our finding suggested that miR-30c-5p might play essential role in NLRP3 inflammasome-modulated cell pyroptosis by targeting FOXO3 in HAECs, providing a novel therapeutic avenue for atherosclerosis treatment.
60 APPLIED LIFE SCIENCES↗
RIP2 deficiency attenuates cardiac hypertrophy, inflammation and fibrosis in pressure overload induced mice
Although the pathological cardiac hypertrophy presents a leading cause of morbidity and mortality worldwide, our knowledge of the molecular mechanisms underlying the disease is still poor. Here, we reported that receptor-interacting serine/threonine-protein kinase 2 (RIP2), promoting pro-inflammatory gene expression, enhanced the pathological cardiac hypertrophy in animals. The effects of RIP2 on the cardiac hypertrophy triggered by pathological stimuli have not been fully investigated. In our study, mice were subjected to aortic banding (AB) surgery to explore the pathological, echocardiographic and molecular mechanisms. RIP2 expressed highly in cardiomyocytes after AB operation in wild type (WT) mice. RIP2-knockout (KO) attenuated cardiac hypertrophy, inflammation and fibrosis in mice 4 weeks after AB-surgery. First, RIP2 knockout down-regulated hypertrophic markers of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and β-myosin heavy chain (β-MHC) in the heart of AB-operated mice.in addition, RIP2-deficiency reduced toll-like receptor 4/myeloid differentiation factor 88/nuclear factor kappa B (TLR4/MyD88/NF-κB) activation, mitogen-activated protein kinases (MAPKs) phosphorylation and transforming growth factor-β1 (TGF-β1)/SMADs expressions, contributing to the suppression of inflammatory response and fibrosis, as further evidenced by down-regulated pro-inflammatory cytokines, including Tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6 and IL-18, as well as fibrosis markers of Collagen I, Collagen III and α-smooth muscle actin (α-SMA). Taken together, our data indicated that RIP2-deficience ameliorated cardiac hypertrophy, inflammation and fibrosis through modulating multiple signaling pathways. - Highlights: • Overexpression of RIP2 contributed to development of hypertrophic heart. • RIP2-knockout attenuates cardiac injury and dysfunction in hypertrophic heart. • RIP2-deficience alleviates inflammation in heart of hypertrophic mice. • RIP2-deletion inhibits fibrosis in the heart of hypertrophic mice.
60 APPLIED LIFE SCIENCES↗
Contact Mechanics of a Small Icosahedral Virus
A virus binding to a surface causes stress of the virus cage near the contact area. Here, we investigate the potential role of substrate-induced structural perturbation in the mechanical response of virus particles to adsorption. This is particularly relevant to the broad category of viruses stabilized by weak noncovalent interactions. We utilize atomic force microscopy to measure height distributions of the brome mosaic virus upon adsorption from solution on atomically flat substrates and present a continuum model that captures our observations and provides estimates of elastic properties and of the interfacial energy of the virus, without recourse to indentation.
59 BASIC BIOLOGICAL SCIENCES↗
Two coexisting liquid phases in switchable ionic liquids
Switchable ionic liquids (SWILs) derived from organic bases and alcohols are attractive due to their applications in gas capture, separations, and nanomaterial synthesis. However, their exact solvent structure still remains a mystery. Here, we present the first chemical mapping of a SWIL solvent structure using in situ time-of-flight secondary ion mass spectrometry. In situ chemical mapping discovers two coexisting liquid phases and molecular structures vastly different from conventional ionic liquids. SWIL chemical speciation is found to be more complex than the known stoichiometry. Dimers and ionic clusters have been identified in SIMS spectra; and confirmed to be the chemical species differentiating from non-ionic liquids via spectral principal component analysis. Our unique in situ molecular imaging has advanced the understanding of SWIL chemistry and how this “heterogeneous” liquid structure may impact SWILs’ physical and thermodynamic properties and associated applications.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Tuning crystallization pathways through sequence engineering of biomimetic polymers
Two-step nucleation pathways in which disordered, amorphous, or dense liquid states precede the appearance of crystalline phases have been reported for a wide range of materials, but the dynamics of such pathways are poorly understood. Moreover, whether these pathways are general features of crystallizing systems or a consequence of system-specific structural details that select for direct versus two-step processes is unknown. Using atomic force microscopy to directly observe crystallization of sequence-defined polymers, we show that crystallization pathways are indeed sequence dependent. When a short hydrophobic region is added to a sequence that directly forms crystalline particles, crystallization instead follows a two-step pathway that begins with the creation of disordered clusters of 10–20 molecules and is characterized by highly non-linear crystallization kinetics in which clusters transform into ordered structures that then enter the growth phase. The results shed new light on non-classical crystallization mechanisms and have implications for the design of self-assembling polymer systems.
36 MATERIALS SCIENCE↗
Analysis of Quasi-periodic Oscillations and Time Lag in Ultraluminous X-Ray Sources with XMM-Newton
We investigated the power density spectrum (PDS) and time lag of ultraluminous X-ray sources (ULXs) observed by XMM-Newton . We determined the PDSs for each ULX and found that five of them show intrinsic variability due to obvious quasi-periodic oscillations (QPOs) of mHz–1 Hz, consistent with previous reports. We further investigated these five ULXs to determine their possible time lag. The ULX QPOs exhibit a soft time lag that is linearly related to the QPO frequency. We discuss the likelihood of the ULX QPOs being type-C QPO analogs, and the time lag models. The ULXs might harbor intermediate-mass black holes if their QPOs are type-C QPO analogs. We suggest that the soft lag and the linearity may be due to reverberation.
79 ASTRONOMY AND ASTROPHYSICS↗
Self-assembly of membrane-like materials from highly stable protein-mimetics
Protein self-assembly is a commonplace phenomenon in living systems and is frequently responsible for building molecular machines that carry out the vast array of functions, such as molecular separation and selective ion transport. Inspired by in nature, various proteins and peptides have been designed and exploited for self-assembly of functional materials in vitro. However, the application of these protein- and peptide-based materials is limited because of their poor stabilities against thermal and chemical degradation. Therefore, there is a great need to develop protein-like synthetic polymers that can function like proteins and peptides for molecular recognition and self-assembly, but exhibit high stabilities. There are several known chemical systems that can create non-natural, sequence-specific polymers, such as ?-peptides and peptoids (poly-N-substituted glycines). Peptoids have received particular attention because they can be cheaply and efficiently synthesized, and several hundred commercially available amines can be used to build their large side-chain diversity. We recently demonstrated that peptoids were able to mimic peptides commonly present in natural biominerals for unprecedented control over both calcite morphology and growth kinetics. In this presentation, we report our progress in exploiting peptoids to mimic proteins and peptides for self-assembly. Specifically, we demonstrate that 12-mer peptoids are able to self-assemble into highly-ordered membrane-like materials both in solution and on substrate surfaces. In aqueous solution, these peptoids self-assemble into highly-crystalline and free-floating nanosheets through a solvent-driven crystallization process. These nanosheets have single-bilayer thickness (3.2 nm) and large area (up to mm2). X-ray diffraction data indicate that these peptoids are highly packed through p-p stacking and peptoid side-chain hydrogen bonding. These results represent the smallest peptoid oligomers that self-assemble into free-floating nanosheets and do not require the compression of monolayers formed at the water-air interface. The formation of single-bilayer-thick nanosheets also occurs on various substrate surfaces. For example, on freshly-cleaved mica surface, we observed that nanosheets were formed through a heterogeneous nucleation process. Similar nanosheets were assembled even when 12-mer peptoids were specifically conjugated with functional groups, indicating that self-assembly of 12-mer peptoids into nanosheets is robust, and these nanosheets can serve as a well-defined 2D platform for post-functionalization. Peptoid self-assembly is highly sequence-specific, and pH sensitive. When the diblock-like 12-mer peptoids are switched to an alternative motif, the resulting 12-mers only self-assemble into fiber-like materials. Multi-scale simulations are also used to provide insights into peptoid-assembly mechanisms
Chen, Chunlong↗
Chemical imaging of molecular changes in a hydrated single cell by dynamic secondary ion mass spectrometry and super-resolution microscopy
Chemical imaging of single cells is important in capturing biological dynamics. Single cell correlative imaging is realized between structured illumination microscopy (SIM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) using System for Analysis at the Liquid Vacuum Interface (SALVI), a multimodal microreactor. SIM characterized cells and guided subsequent ToF-SIMS analysis. Dynamic ToF-SIMS provided time- and space-resolved cell molecular mapping. Lipid fragments were identified in the hydrated cell membrane. Principal component analysis was used to elucidate chemical component differences among mouse lung cells that uptake zinc oxide nanoparticles. Our results provided submicron chemical spatial mapping for investigations of cell dynamics at the molecular level.
correlative chemical imaging • microfluidic • surf↗