Polysaccharide-Based Injectable Hydrogels with Fast Gelation and Self-Strengthening Mechanical Kinetics for Oral Tissue Regeneration.

Oral defects lead to a series of function disorders, severely threatening the patients' health. Although injectable hydrogels are widely studied in tissue regeneration, their mechanical performance is usually stationary after implant, without further self-adaption toward the microenvironment. Herein, an injectable hydrogel with programmed mechanical kinetics of instant gelation and gradual self-strengthening along with outstanding biodegradation ability is developed. The fast gelation is realized through rapid Schiff base reaction between biodegradable chitosan and aldehyde-modified sodium hyaluronate, while self-strengthening is achieved via slow reaction between redundant amino groups on chitosan and epoxy-modified hydroxyapatite. The resultant hydrogel also possesses multiple functions including (1) bio-adhesion, (2) self-healing, (3) bactericidal, (4) hemostasis, and (5) X-ray in situ imaging, which can be effectively used for oral jaw repair. We believe that the strategy illustrated here will provide new insights into dynamic mechanical regulation of injectable hydrogels and promote their application in tissue regeneration.

Formation mechanism of typical aromatic sulfuric anhydrides and their potential role in atmospheric nucleation process.

Sulfuric anhydrides, generated from the cycloaddition reaction of SO3 with carboxylic acids, have been revealed to be potential participants in the nucleation process of new particle formation (NPF). Hence the reaction mechanisms of typical aromatic acids (benzoic acid (BA), phenylacetic acid (PAA), phthalic acid (PA), isophthalic acid (mPA), and terephthalic acid (PTA)) with SO3 to generate the corresponding aromatic sulfuric anhydrides were investigated by density functional theory calculations at the level of M06-2X/6-311++G(3df,3pd). As a result, these reactions were found to be feasible in the gas phase with barriers of 0.34, 0.30, 0.18, 0.08 and 0.12 kcal/mol to generate corresponding aromatic sulfuric anhydrides, respectively. The thermodynamic stabilities of clusters containing aromatic sulfuric anhydrides and atmospheric nucleation precursors (sulfuric acid, ammonia and dimethylamine) were further analyzed to identify the potential role of aromatic sulfuric anhydrides in NPF. As the thermodynamic stability of a cluster depends on both the number and strength of hydrogen bonds, the greater stability of the interactions between atmospheric nucleation precursors and aromatic sulfuric anhydrides than with aromatic acids make aromatic sulfuric anhydrides potential participators in the nucleation process of NPF. Moreover, compared with BA, the addition of a -CH2- functional group in PAA has little influence on the reaction barrier with SO3 but an inhibitive effect on the thermodynamic stability of clusters. The position of the two -COOH functional groups in PA, mPA and PTA does not have a consistent impact on the reaction barrier with SO3 or the thermodynamic stability.

Molecular characterization of size-segregated organic aerosols in the urban boundary layer in wintertime Beijing by FT-ICR MS.

Organic aerosols, complicated mixtures of organic compounds, are important constituents of atmospheric particulate matter. However, little is known about the size distributions and vertical profiles of these constituents at a molecular level in the urban boundary layer. Here, we characterized the molecular compositions of size-segregated samples collected simultaneously at two heights (8 m and 260 m above ground level) in urban Beijing during the winter of 2018. The CHO, CHNO, CHOS, and CHNOS subgroups in water-soluble organic carbon were characterized using a 15-T ultrahigh-resolution Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer. We found that both their numbers and magnitudes increased with a decrease in the particle size, especially for high molecular weight (HMW) compounds, except CHNOS. The number of CHNOS species also increased in the coarse mode, presumably because the alkalinity could inhibit their hydrolysis in the coarse mode. The compounds in small particles with higher O/C ratios and carbon oxidation state were possibly more aged, while the coarse particles with more lipid- and peptide-like compounds should originate from fresh emissions. Moreover, as the oxidation state increases in small particles, functionalization is enhanced for sulfur-containing compounds with fracturing of the benzene ring, while CHO and CHNO are potentially dominated by demethylation with ring-retaining products. It is worth noting that common compounds with the same molecular characteristics accounted for more than 86% of the total compounds between 260 m and ground level (8 m), demonstrating that the aerosols were well mixed in the urban boundary layer. Nonetheless, the relative content of the compounds was higher at ground level due to the impact of primary emissions, which increased with the particle size. In addition, the compounds in submicron particles were more oxidized at 260 m, while the opposite was observed in the coarse mode.

High Molecular Diversity of Organic Nitrogen in Urban Snow in North China.

Snow serves as a vital scavenging mechanism to gas-phase and particle-phase organic nitrogen substances in the atmosphere, providing a significant link between land-atmosphere flux of nitrogen in the surface-earth system. Here, we used optical instruments (UV-vis and excitation-emission matrix fluorescence) and a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) to elucidate the molecular composition and potential precursors of snow samples collected simultaneously at four megacities in North China. The elemental O/N ratio (≥3), together with the preference in the negative ionization mode, indicates that the one and two nitrogen atom-containing organics (CHON1 and CHON2) in snow were largely in the oxidized form (as organic nitrates, -ONO2). This study assumed that scavenging of particle-phase and gas-phase organic nitrates might be significant sources of CHON in precipitation. A gas-phase oxidation process and a particle-phase hydrolysis process, at a molecular level, were used to trace the potential precursors of CHON. Results show that more than half of the snow CHON molecules may be related to the oxidized and hydrolyzed processes of atmospheric organics. Potential formation processes of atmospheric organics on a molecular level provide a new concept to better understand the sources and scavenging mechanisms of organic nitrogen species in the atmosphere.

Evaluation of renewable pH-responsive starch-based flocculant on treating and recycling of highly saline textile effluents.

Herein, we report a novel renewable pH-responsive starch-based flocculant (CIAT-ST) via etherifying 2-chloro-4,6-isopropylamino-[1,3,5]-triazine (CIAT) onto the starch backbones for decontamination and reuse of highly saline effluents. The obtained CIAT-ST shows a unique pH-sensibility and reversibility in response to a subtle pH change due to a pH-controllable surface charge density of polymer chains. The level of residual CIAT-ST in the solution can be facilely monitored by using UV-vis detection. The dye flocculation performance of CIAT-ST was evaluated by using a batch experiment. The results exhibited that the dye removal was highly dependent on the solution pH (optimal pH was 2), the flocculation equilibrium can be achieved within 5 min, and the maximum flocculation capacity of CIAT-ST for K-2BP and KN-B5 were calculated to be 2452.6 ± 23.9 and 792.7 ± 14.1 mg/g, respectively. The multiple flocculation mechanisms, including charge neutralization, bridging and charge patching, may participate in the flocculation process. Adjustment in pH-mediated hydrophilicity-hydrophobicity switch of flocculant facilitates readily recovery and then sequentially reused three times while retaining satisfying flocculation efficiency. A significant contribution was also confirmed that the highly saline effluents after flocculation and sedimentation were reused in three successive dyeing processes without sacrificing fabric quality (ΔE* < 1) due to relatively low polymer residuals, and the efficiency of salt reuse for consecutive regeneration processes could be achieved above 85%. The present work could provide alternative thoughts for the reutilization of spent flocculant and clarified saline wastewater, which is also an efficient and sustainable strategy for textile wastewater management.

Selective Protein Separation Based on Charge Anisotropy by Spherical Polyelectrolyte Brushes.

Protein purification is of vital importance in the food industry, drug discovery, and other related fields. Among many separation methods, polyelectrolyte (PE)-based phase separation was developed and recognized as a low-cost purification technique. In this work, spherical polyelectrolyte brushes (SPBs) with a high specific surface area were utilized to study the protein accessibility and selective protein binding on highly charged nanoparticles (NPs) as well as the selective phase separation of proteins. The correlation between charge anisotropy, protein binding, and phase separation was investigated on various protein systems including those proteins with similar isoelectric points (pI) such as bovine serum albumin (BSA) and ß-lactoglobulin (BLG), proteins with similar molecular weights such as BSA and hemoglobin (HB), and even protein variants (BLG-A and -B) with a tiny difference of amino acids. The nonspecific electrostatic interaction studied by turbidimetric titrations and isothermal calorimetry titration (ITC) indicates a specific binding between proteins and SPBs arising from the charge anisotropy of proteins. An optimized output based on selective protein binding on SPBs could be correlated for efficient protein separation through tuning external conditions including pH and ionic strength. These findings, therefore, proved that phase separation based on selective protein adsorption by SPBs was an efficient alternative for protein separation compared with the traditional practice.

Overt social interaction and resting state in young adult males with autism: core and contextual neural features.

Conversation is an important and ubiquitous social behaviour. Individuals with autism spectrum disorder (autism) without intellectual disability often have normal structural language abilities but deficits in social aspects of communication like pragmatics, prosody, and eye contact. Previous studies of resting state activity suggest that intrinsic connections among neural circuits involved with social processing are disrupted in autism, but to date no neuroimaging study has examined neural activity during the most commonplace yet challenging social task: spontaneous conversation. Here we used functional MRI to scan autistic males (n = 19) without intellectual disability and age- and IQ-matched typically developing control subjects (n = 20) while they engaged in a total of 193 face-to-face interactions. Participants completed two kinds of tasks: conversation, which had high social demand, and repetition, which had low social demand. Autistic individuals showed abnormally increased task-driven interregional temporal correlation relative to controls, especially among social processing regions and during high social demand. Furthermore, these increased correlations were associated with parent ratings of participants' social impairments. These results were then compared with previously-acquired resting state data (56 autism, 62 control subjects). While some interregional correlation levels varied by task or rest context, others were strikingly similar across both task and rest, namely increased correlation among the thalamus, dorsal and ventral striatum, somatomotor, temporal and prefrontal cortex in the autistic individuals, relative to the control groups. These results suggest a basic distinction. Autistic cortico-cortical interactions vary by context, tending to increase relative to controls during task and decrease during test. In contrast, striato- and thalamocortical relationships with socially engaged brain regions are increased in both task and rest, and may be core to the condition of autism.

Preparation of Electrospun Gelatin Mat with Incorporated Zinc Oxide/Graphene Oxide and Its Antibacterial Activity.

Current wound dressings have poor antimicrobial activities and are difficult to degrade. Therefore, biodegradable and antibacterial dressings are urgently needed. In this article, we used the hydrothermal method and side-by-side electrospinning technology to prepare a gelatin mat with incorporated zinc oxide/graphene oxide (ZnO/GO) nanocomposites. The resultant fibers were characterized by field emission environment scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). Results indicated that the gelatin fibers had good morphology, and ZnO/GO nanocomposites were uniformly dispersed on the fibers. The loss of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) viability were observed to more than 90% with the incorporation of ZnO/GO. The degradation process showed that the composite fibers completely degraded within 7 days and had good controllable degradation characteristics. This study demonstrated the potential applicability of ZnO/GO-gelatin mats with excellent antibacterial properties as wound dressing material.

Interactions of sulfuric acid with common atmospheric bases and organic acids: Thermodynamics and implications to new particle formation.

Interactions of the three common atmospheric bases, dimethylamine ((CH3)2NH), methylamine (CH3NH2), ammonia (NH3), all considered to be efficient stabilizers of binary clusters in the Earth's atmosphere, with H2SO4, the key atmospheric precursor, and 14 common atmospheric organic acids (COAs) (formic, acetic, oxalic, malonic, succinic, glutaric acid, adipic, benzoic, phenylacetic, pyruvic, maleic acid, malic, tartaric and pinonic acids) have been studied using the density functional theory (DFT) and composite high-accuracy G3MP2 method. The thermodynamic stability of mixed (COA)(H2SO4), (COA)(B1), (COA)(B2) and (COA)(B3) dimers and (COA)(H2SO4)(B1), (COA)(H2SO4)(B2) and (COA)(H2SO4)(B3) trimers, where B1, B2 and B3 refer to (CH3)2NH, CH3NH2 and NH3, respectively, have been investigated and their impacts on the thermodynamic stability of clusters containing H2SO4 have been studied. Our investigation shows that interactions of H2SO4 with COA, (CH3)2NH, CH3NH2 and NH3 lead to the formation of more stable mixed dimers and trimers than (H2SO4)2 and (H2SO4)2(base), respectively, and emphasize the importance of common organic species for early stages of atmospheric nucleation. We also show that although amines are generally confirmed to be more active than NH3 as stabilizers of binary clusters, in some cases mixed trimers containing NH3 are more stable thermodynamically than those containing CH3NH2. This study indicates an important role of COA, which coexist and interact with that H2SO4 and common atmospheric bases in the Earth atmosphere, in formation of stable pre-nucleation clusters and suggests that the impacts of COA on new particle formation (NPF) should be studied in further details.

Transient species in the ozonolysis of tetramethylethene.

The reaction of alkenes with ozone has great effect on atmospheric oxidation, its transient species can produce OH radicals and contribute to the formation of secondary organic aerosols (SOA). In the present study, the reaction of tetramethylethene (TME) with ozone was investigated using self-assembled low temperature matrix isolation system. The TME and ozone were co-deposited on a salt plate at 15 K, and then slowly warmed up the plate. The first transient species primary ozonide (POZ) was detected, indicating that the reaction followed Criegee mechanism. Then POZ began to decompose at 180 K. However, secondary ozonide (SOZ) was not observed according to Criegee mechanism. Probably, Criegee Intermediate (CI) did not react with inert carbonyl of acetone, but with remaining TME formed tetra-methyl epoxide (EPO).

Decrease of MiR-31 induced by TNF-α inhibitor activates SATB2/RUNX2 pathway and promotes osteogenic differentiation in ethanol-induced osteonecrosis.

PURPOSE: Suppressed osteogenic differentiation is considered a main cause of ethanol-induced osteonecrosis. Tumor necrosis factor α (TNF-α) and miR-31 have been reported to be involved in the osteogenic induction. This study aimed to explore a possible molecular mechanism regulating osteogenic differentiation in ethanol-induced osteonecrosis bone marrow stromal stem cells (BMSCs). METHODS: Alizarin red staining was used to examine the level of mineralization in osteogenic differentiation process. Alkaline phosphatase assay was applied to the validation of ALP level which was essential to bone mineralization. The level of osteogenesis markers was determined by western blot assay, whereas the fluctuations of messenger RNA levels were tested by quantitative real-time polymerase chain reaction. Microarray analysis was conducted to identify differentially expressed genes, because the possible target relationship was predicted and validated by miRBase and luciferase reporter assay, respectively. Colony forming unit of fibroblast assay was used to observe the proliferation of BMSCs. RESULTS: BMSCs from patients with ethanol-induced osteonecrosis exhibited weaker osteogenic differentiation and proliferation abilities. TNF-α inhibitor added in the osteogenic medium significantly enhanced the osteogenic differentiation ability and BMSCs proliferation ability. TNF-α by regulating miR-31 downregulated the expressions of RUNX2 and SATB2, two contributors of osteoblast differentiation, further suppressed osteogenic differentiation. On the contrary, TNF-α inhibitor could promote osteogenic differentiation in BMSCs from patients with ethanol-induced osteonecrosis. CONCLUSION: TNF-α inhibitor could downregulate miR-31 expressions, which directly promoted SATB2 and RUNX2 expressions and enhanced osteogenic differentiation of BMSCs from patients with ethanol-induced osteonecrosis.

Ratiometric Nanoparticle Array-Based Near-Infrared Fluorescent Probes for Quantitative Protein Sensing.

Quantitative detection of protein biomarkers is crucial to medical diagnosis. Fluorescent probes have been frequently used for protein detection, but they suffered from various weaknesses such as lack of versatility. In particular, most of the reported probes were not capable of simultaneous qualitative and quantitative detection for various proteins. In this paper, we developed novel nanoparticle array-based near-infrared (NIR) ratiometric probes for potent protein analysis, in which the specific protein was able to be distinguished and quantitated within a group of 11 common proteins. The activity of ß-galactosidases (ß-gal) was temporarily inhibited by the adsorption to magnetic nanoparticles and restored to certain content by replacement with detected proteins, leading to distinctive readout of the enzyme-activatable NIR probe (DCM-ß-gal). The readout of the sensor array against 11 proteins, as verified by isothermal titration calorimetry, was processed and transformed into canonical factors with the help of linear discrimination analysis. Moreover, the ratiometric signals of DCM-ß-gal were translated to quantitatively detect proteins within the concentration range of 0-100 µg/mL. Based on clear differentiation within both two-dimensional and three-dimensional plots, different proteins could be detected with 100% accuracy with their concentration simultaneously determined, which endowed the sensing system with great potential in clinical diagnosis.

Three-Dimensional Printed Titanium Scaffolds Enhance Osteogenic Differentiation and New Bone Formation by Cultured Adipose Tissue-Derived Stem Cells Through the IGF-1R/AKT/Mammalian Target of Rapamycin Complex 1 (mTORC1) Pathway.

BACKGROUND This study aimed to investigate the effects of three-dimensional (3D) printed titanium (3DTi) scaffolds on osteogenic differentiation and new bone formation by 3D cultured adipose tissue-derived stem cells (ADSCs) in vitro, and the effects of bone regeneration in vivo using a full-thickness mandibular defect rat model, and the mechanisms involved. MATERIAL AND METHODS Alpha-beta titanium alloy (Ti6Al4V) 3DTi scaffolds were prepared with Cellmatrix hydrogel and 3D culture medium. ADSCs were impregnated into the 3DTi scaffolds. ADSC viability and proliferation were assessed using the cell counting kit-8 (CCK-8) assay, and alkaline phosphatase (ALP) levels were measured. Real-time polymerase chain reaction (RT-PCR) and Western blot were performed to assess the expression of osteogenesis-related mRNA for RUNX2, OPN, OCN, and IGF-1 genes and proteins. A rat model of full-thickness mandibular defect was evaluated with micro-computed tomography (microCT) scanning, and histochemistry with Alizarin red and von Giesen's stain were used to evaluate osteogenesis. RESULTS ADSC viability and proliferation were not affected by culture with 3DTi scaffolds. Expression of osteogenesis-related mRNA and proteins for RUNX2, OPN, OCN, and IGF-1, expression of ALP, and histochemical findings showed that the use of 3DTi scaffolds enhanced osteogenic differentiation and new bone formation by ADSCs, with upregulation of components of the IGF-1R/AKT/mTORC1 pathway. CONCLUSIONS The 3D culture of ADSCs with 3DTi scaffolds enhanced osteogenic differentiation and new bone formation through the IGF-1R/AKT/mTORC1 pathway. This improved method of osteointegration may have clinical application in the preparation of bone grafts before implantation for improved repair of mandibular bone defects.

Photoactivation of Ligands for Extrinsically and Intrinsically Triggered Disassembly of Amphiphilic Nanoassemblies.

Specific response to the concurrent presence of two different inputs is one of the hallmarks of incorporating specificities in nature. Artificial nanoassemblies that concurrently respond to two very different inputs are of great interest in a variety of applications, especially in biomedicine. Here, we present a design strategy for amphiphilic nanoassemblies with such capabilities, enabled by photocaging a ligand moiety that is capable of binding to a specific protein. New molecular designs that offer nanoassemblies that respond to either of two inputs or only to the concurrent presence of two inputs are outlined. Such biomimetic nanoassemblies could find use in many applications, including drug delivery and diagnostics.

Ionic Strength-Responsive Binding between Nanoparticles and Proteins.

Electrostatic interaction is a strong, dominant nonspecific interaction which was extensively studied in protein-nanoparticle (NP) interactions [ Lounis , F. M. ; J. Phys. Chem. B 2017 , 121 , 2684 - 2694 ; Tavares , G. M. ; Langmuir 2015 , 31 , 12481 - 12488 ; Antonov , M. ; Biomacromolecules 2010 , 11 , 51 - 59 ], whereas the role of hydrophobic interaction arising from the abundant hydrophobic residues of globule proteins upon protein-NP binding between the proteins and charged nanoparticles has rarely been studied. In this work, a series of positively charged magnetic nanoparticles (MNPs) were prepared via atom transfer radical polymerization and surface hydrophobicity differentiation was achieved through postpolymerization quaternization by different halohydrocarbons. The ionic strength- and hydrophobicity-responsive binding of these MNPs toward ß-lactoglobulin (BLG) was studied by both qualitative and quantitative methods including turbidimetric titration, dynamic light scattering, and isothermal titration calorimetry. Judged from the critical binding pH and binding constant for MNP-BLG complexation, the dependence of binding affinity on surface hydrophobicity exhibited an interesting shift with increasing ionic strength, which means that the MNPs with higher surface hydrophobicity exhibits weaker binding affinity at lower ionic strength but stronger affinity at higher ionic strength. This interesting observation could be attributed to the difference in ionic strength responsiveness for hydrophobic and electrostatic interactions. In this way, the well-tuned binding pattern could be achieved with optimized binding affinity by controlling the surface hydrophobicity of MNPs and ionic strength, thus endowing this system with great potential to fabricate separation and delivery system with high selectivity and efficiency.

Real-Time Tracking and In Vivo Visualization of ß-Galactosidase Activity in Colorectal Tumor with a Ratiometric Near-Infrared Fluorescent Probe.

Development of "smart" noninvasive bioimaging probes for trapping specific enzyme activities is highly desirable for cancer therapy in vivo. Given that ß-galactosidase (ß-gal) is an important biomarker for cell senescence and primary ovarian cancers, we design an enzyme-activatable ratiometric near-infrared (NIR) probe (DCM-ßgal) for the real-time fluorescent quantification and trapping of ß-gal activity in vivo and in situ. DCM-ßgal manifests significantly ratiometric and turn-on NIR fluorescent signals simultaneously in response to ß-gal concentration, which makes it favorable for monitoring dynamic ß-gal activity in vivo with self-calibration in fluorescent mode. We exemplify DCM-ßgal for the ratiometric tracking of endogenously overexpressed ß-gal distribution in living 293T cells via the lacZ gene transfection method and OVCAR-3 cells, and further realize real-time in vivo bioimaging of ß-gal activity in colorectal tumor-bearing nude mice. Advantages of our system include light-up ratiometric NIR fluorescence with large Stokes shift, high photostability, and pH independency under the physiological range, allowing for the in vivo real-time evaluation of ß-gal activity at the tumor site with high-resolution three-dimensional bioimaging for the first time. Our work provides a potential tool for in vivo real-time tracking enzyme activity in preclinical applications.

Adsorption of Lysine on Na-Montmorillonite and Competition with Ca(2+): A Combined XRD and ATR-FTIR Study.

Lysine adsorption at clay/aqueous interfaces plays an important role in the mobility, bioavailability, and degradation of amino acids in the environment. Knowledge of these interfacial interactions facilitates our full understanding of the fate and transport of amino acids. Here, X-ray diffraction (XRD) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) measurements were used to explore the dynamic process of lysine adsorption on montmorillonite and the competition with Ca(2+) at the molecular level. Density functional theory (DFT) calculations were employed to determine the peak assignments of dissolved lysine in the solution phase. Three surface complexes, including dicationic, cationic, and zwitterionic structures, were observed to attach to the clay edge sites and penetrate the interlayer space. The increased surface coverage and Ca(2+) competition did not affect the interfacial lysine structures at a certain pH, whereas an elevated lysine concentration contributed to zwitterionic-type coordination at pH 10. Moreover, clay dissolution at pH 4 could be inhibited at a higher surface coverage with 5 and 10 mM lysine, whereas the inhibition effect was inconspicuous or undetected at pH 7 and 10. The presence of Ca(2+) not only could remove a part of the adsorbed lysine but also could facilitate the readsorption of dissolved Si(4+) and Al(3+) and surface protonation. Our results provide new insights into the process of lysine adsorption and its effects on montmorillonite surface sites.

Construction of Compact Polyelectrolyte Multilayers Inspired by Marine Mussel: Effects of Salt Concentration and pH As Observed by QCM-D and AFM.

Biomimetic multilayers based on layer-by-layer (LbL) assembly were prepared as functional films with compact structure by incorporating the mussel-inspired catechol cross-linking. Dopamine-modified poly(acrylic acid) (PAADopa) was synthesized as a polyanion to offer electrostatic interaction with the prelayer polyethylenimine (PEI) and consecutively cross-linked by zinc to generate compact multilayers with tunable physicochemical properties. In situ layer-by-layer growth and cross-linking were monitored by a quartz crystal microbalance with dissipation (QCM-D) to reveal the kinetics of the process and the influence of Dopa chemistry. Addition of Dopa enhanced the mass adsorption and led to the formation of a more compact structure. An increase of ionic strength induced an increase in mass adsorption in the Dopa-cross-linked multilayers. This is a universal approach for coating of various surfaces such as Au, SiO2, Ti, and Al2O3. Roughness observed by AFM in both wet and dry conditions was compared to confirm the compact morphology of Dopa-cross-linked multilayers. Because of the pH sensitivity of Dopa moiety, metal-chelated Dopa groups can be turned into softer structure at higher pH as revealed by reduction of Young's modulus determined by MFP-3D AFM. A deeper insight into the growth and mechanical properties of Dopa-cross-linked polyelectrolyte multilayers was addressed in the present study. This allows a better control of these systems for bioapplications.

Molecular-Scale Study of Aspartate Adsorption on Goethite and Competition with Phosphate.

Knowledge of the interfacial interactions between aspartate and minerals, especially its competition with phosphate, is critical to understanding the fate and transport of amino acids in the environment. Adsorption reactions play important roles in the mobility, bioavailability, and degradation of aspartate and phosphate. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) measurements and density functional theory (DFT) calculations were used to investigate the interfacial structures and their relative contributions in single-adsorbate and competition systems. Our results suggest three dominant mechanisms for aspartate: bidentate inner-sphere coordination involving both α- and γ-COO(-), outer-sphere complexation via electrostatic attraction and H-bonding between aspartate NH2 and goethite surface hydroxyls. The interfacial aspartate is mainly governed by pH and is less sensitive to changes of ionic strength and aspartate concentration. The phosphate competition significantly reduces the adsorption capacity of aspartate on goethite. Whereas phosphate adsorption is less affected by the presence of aspartate, including the relative contributions of diprotonated monodentate, monoprotonated bidentate, and nonprotonated bidentate structures. The adsorption process facilitates the removal of bioavailable aspartate and phosphate from the soil solution as well as from the sediment pore water and the overlying water.

Rhythmic alternating patterns of brain activity distinguish rapid eye movement sleep from other states of consciousness.

Rapid eye movement (REM) sleep constitutes a distinct "third state" of consciousness, during which levels of brain activity are commensurate with wakefulness, but conscious awareness is radically transformed. To characterize the temporal and spatial features of this paradoxical state, we examined functional interactions between brain regions using fMRI resting-state connectivity methods. Supporting the view that the functional integrity of the default mode network (DMN) reflects "level of consciousness," we observed functional uncoupling of the DMN during deep sleep and recoupling during REM sleep (similar to wakefulness). However, unlike either deep sleep or wakefulness, REM was characterized by a more widespread, temporally dynamic interaction between two major brain systems: unimodal sensorimotor areas and the higher-order association cortices (including the DMN), which normally regulate their activity. During REM, these two systems become anticorrelated and fluctuate rhythmically, in reciprocally alternating multisecond epochs with a frequency ranging from 0.1 to 0.01 Hz. This unique spatiotemporal pattern suggests a model for REM sleep that may be consistent with its role in dream formation and memory consolidation.