Neutral Core Research Articles

Blood Components Interactions to Ionic and Nonionic Glyconanogels.

Nanogels are prominent examples of "smart" nanomaterials, which are designed to incorporate biologically relevant (macro)molecules for systemic delivery. Although these systems are carefully engineered, only a handful of studies discuss the blood compatibility of nanogels, and no systematic studies are available on how the presence of net or surface charges impacts the hemocompatibility of these nanomaterials. Therefore, in this study, temperature responsive, galactose based nanogels bearing net positive, negative, or neutral charges, either in the core or shell of nanogels, are prepared and are subsequently evaluated for their blood compatibility profiles. The nanogels containing neutral core and shell, cationic core with neutral shell, anionic core with neutral shell, neutral core with cationic shell, and neutral core with anionic shell are prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization approach. The evaluation of complement activation, blood clot formation, platelet activation, red blood cells aggregation, and hemolysis provides a detailed analysis of structure activity relationship of blood compatibility profile of these nanogels. The data reveal that the physical and biological (blood compatibility) properties can be carefully tuned by embedding the charges in the core of temperature-responsive nanomaterials, protected by neutral carbohydrate based shells.

Reconstitution of Adiposome and Artificial Lipid Droplets

The Lipid droplet (LD) is a cellular organelle that consists of a neutral lipid core with a phospholipid monolayer membrane associated with proteins. The presence of this organelle in organisms ranging from bacteria to humans demonstrates that it is highly conserved and may be the first membrane‐bound organelle in living organisms. Recent progress in LD research demonstrates its important roles in energy homeostasis and metabolic syndromes. However, the mechanisms governing its formation, dynamics, interaction with other cellular organelles, and association with proteins have remained elusive. Therefore, we developed an in vitro system to facilitate the elucidation of these mechanisms, based on the reconstitution of artificial LDs. First, we generated sphere‐shaped structures with a neutral lipid core and phospholipid monolayer membrane by mechanically mixing neutral lipids and phospholipids followed by two‐step purification. Since the artificial lipid vesicle, a double layer phospholipid membrane structure, is termed as “liposome”, we named this monolayer phospholipid membrane‐bound structure “adiposome”. We then recruited LD structure‐like/resident proteins to the adiposome, including the bacterial LD protein MLDS, C. elegans LD protein MDT‐28, or mammalian LD protein ADRP/PLIN2. We term the functional protein‐coated adiposomes, “artificial lipid droplets”. Using this experimental system, different proteins can be recruited to build artificial LDs for myriad biological and medical goals.

A NEW BLACK HOLE MASS ESTIMATE FOR OBSCURED ACTIVE GALACTIC NUCLEI

We propose a new method for estimating the mass of a supermassive black hole, applicable to obscured AGNs. This method estimates the black hole mass using the width of the narrow core of the neutral FeKa emission line in X-rays and the distance of its emitting region from the black hole based on the isotropic luminosity indicator via the luminosity scaling relation. We collect the line width data of the neutral FeKa line core for seven type-1 AGNs and seven type-2 AGNs obtained by the Chandra HETGS. Assuming the virial relation between the locations and the velocity widths of the neutral FeKa line core and the broad Hb emission line, the luminosity scaling relation of the neutral FeKa line core emitting region is estimated. We find that the FWHM of the neutral FeKa line core falls between that of the broad Balmer emission lines and the corresponding value at the dust reverberation radius for most of the type-1 AGNs and for all of the type-2 AGNs. This suggests that significant fraction of photons of the neutral FeKa line core originates between the outer BLR and the inner dust torus in most cases. The black hole mass M_FeKa estimated with this method is then compared with other black hole mass estimates, such as the broad emission-line reverberation mass M_rev for the type-1 AGNs, the mass M_H2O based on the H2O maser and the single-epoch mass estimate M_pol based on the polarized broad Balmer lines for the type-2 AGNs. We find that M_FeKa is consistent with M_rev for the most of the type-1 AGNs and with M_pol for all of the type-2 AGNs. We also find that M_FeKa is correlated well with M_H2O for the type-2 AGNs. These results suggest that M_FeKa is a potential indicator of the black hole mass especially for obscured AGNs. In contrast, M_FeKa for which the same virial factor as for M_rev and M_pol is adopted is systematically larger than M_H2O by about a factor of about 5. (abridged)

Comparison of Follicle-Stimulating Hormone Glycosylation Microheterogenity by Quantitative Negative Mode Nano-Electrospray Mass Spectrometry of Peptide-N Glycanase-Released Oligosaccharides.

Glycans from six highly purified hFSH preparations were released by peptide-N-glycanase digestion and analyzed by negative mode nano-ESI mass spectrometry before and after neuraminidase digestion. Pituitary glycan structures were mainly high-mannose, di-, tri-, and tetra-antennary, and their abundance largely paralleled that reported by other investigators using different approaches. For most of the FSH preparations, the differences in glycosylation appeared to be restricted to relative abundances of the major glycan families, as defined by their neutral core oligosaccharide structures. Qualitative differences between glycan populations were largely relegated to those species that were lowest in abundance. Significant qualitative differences were noted in two cases. Recombinant GH3-hFSH triantennary glycans appeared to have the third antenna exclusively on the mannose6-branch, in contrast to all pituitary and urinary hFSH triantennary glycans, in which this antenna was exclusively attached to the mannose3-branch. The hypo-glycosylated hFSH preparation isolated from purified hLH was decorated with high mannose glycans that accounted for over 40% of the total in this population. As this preparation was found to be consistently 20-fold more active than hFSH24 in FSH receptor-binding assays, it appears that both macroheterogeneity and microheterogeneity in FSH preparations need to be taken into account.

ON THE ONSET OF SECONDARY STELLAR GENERATIONS IN GIANT STAR-FORMING REGIONS AND MASSIVE STAR CLUSTERS

Here we consider the strong evolution experienced by the matter reinserted by massive stars, both in giant star forming regions driven by a constant star formation rate, and in massive and coeval superstar clusters. In both cases we take into consideration the changes induced by stellar evolution on the number of massive stars, the number of ionizing photons and the integrated mechanical luminosity of the star forming regions. The latter is at all times compared with the critical luminosity that defines, for a given size, the lower mechanical luminosity limit above which the matter reinserted via strong winds and supernova explosions suffers frequent and recurrent thermal instabilities that reduce its temperature and pressure and inhibit its exit as part of a global wind. Instead, the unstable reinserted matter is compressed by the pervasive hot gas, and photoionization maintains its temperature at T $\sim$ 10$^4$ K. As the evolution proceeds, more unstable matter accumulates and the unstable clumps grow in size. Here we evaluate the possible self-shielding of thermally unstable clumps against the UV radiation field. Self shielding allows for a further compression of the reinserted matter which rapidly develops a high density neutral core able to absorb in its outer skin the incoming UV radiation. Under such conditions the cold (T $\sim$ 10 K) neutral cores soon surpass the Jeans limit and become gravitationally unstable, causing a new stellar generation with the matter reinserted by former massive stars. We present the results of several calculations of this positive star formation feedback scenario promoted by strong radiative cooling and mass loading.

The proteome of cholesteryl-ester-enriched versus triacylglycerol-enriched lipid droplets.

Within cells, lipids are stored in the form of lipid droplets (LDs), consisting of a neutral lipid core, surrounded by a phospholipid monolayer and an outer layer of protein. LDs typically accumulate either triacylglycerol (TAG) and diacylglycerol or cholesteryl ester (CE), depending on the type of tissue. Recently, there has been an increased interest in the proteins that surround LDs. LD proteins have been found to be quite diverse, from structural proteins to metabolic enzymes, proteins involved in vesicular transport, and proteins that may play a role in LD formation. Previous proteomics analyses have focused on TAG-enriched LDs, whereas CE-enriched LDs have been largely ignored. Our study has compared the LD proteins from CE-enriched LDs to TAG-enriched LDs in steroidogenic cells. In primary rat granulosa cells loaded with either HDL to produce CE-enriched LDs or fatty acids to produce TAG-enriched LDs, 61 proteins were found to be elevated in CE-enriched LDs and 40 proteins elevated in TAG-enriched LDs with 278 proteins in similar amounts. Protein expression was further validated by selected reaction monitoring (SRM) mass spectrometry (MS). SRM verified expression of 25 of 27 peptides that were previously detected by tandem mass tagging MS. Several proteins were confirmed to be elevated in CE-enriched LDs by SRM including the intermediate filament vimentin. This study is the first to compare the proteins found on CE-enriched LDs with TAG-enriched LDs and constitutes the first step in creating a better understanding of the proteins found on CE-enriched LDs in steroidogenic cells.

Bis(dimethylphosphino)methane-ligated silver chloride, cyanide and hydride cluster cations: Synthesis and gas-phase unimolecular reactivity

Electrospray ionization mass spectrometry (ESI/MS) of mixtures of AgNO3 or AgBF4 with the capping ligand Me2P(CH2)PMe2 (dmpm, L) in a solution of 1:1 methanol:chloroform or acetonitrile revealed the formation of: dinuclear clusters [Ag2L2]2+, [Ag2(LH)L]+, and [Ag2ClL2]+; trinuclear clusters primarily as [Ag3Cl2L3]+; and the tetranuclear cluster [Ag4Cl3L3]+. Addition of NaBH4 to these solutions of dmpm-protected clusters results in the formation of the silver hydride cluster cations [Ag2HL2]+, [Ag3HL3]2+, [Ag3HL4]2+, [Ag3H(CN)L3]+ and [Ag3HClL3]+ as determined by ESI/MS. Use of NaBD4 confirmed that the borohydride is the source of the hydride in these clusters.The gas-phase unimolecular chemistry of selected clusters was examined in a LTQ-FT hybrid linear ion trap (LIT) mass spectrometer. Low-energy collision-induced dissociation (CID) was performed on the clusters [Ag3Cl2L3]+, [Ag3HClL3]+, [Ag3H(CN)L3]+, [Ag3HL3]2+, [Ag3HL4]2+ and their nascent fragments. Neutral ligand loss, core fission and ligand activation were observed to depend on the cluster stoichiometry. Thus, [Ag3XYL3]+ (X, Y=Cl; X=H; Y=Cl or CN) mainly fragment via ligand loss, [Ag3XYL2]+ undergoes both ligand loss and core fission, [Ag3XYL]+ undergoes core fission and [Ag2YL]+ undergoes ligand activation. Small yields of reductive elimination of HY are observed for [Ag3HYL2]+ (Y=Cl and CN). Density functional theory (DFT) calculations were used to calculate the energetics of the optimised structures for all parent, fragment ions and neutrals and to estimate the reaction endothermicities. Generally there is a reasonable agreement between the most abundant product ion formed and the predicted endothermicity, except for the reductive elimination reactions. Finally, electron-induced dissociation (EID) of [Ag3HL3]2+ and [Ag3HL4]2+ gave similar fragmentation channels to CID.

Dyslipidemia in Insulin Resistance: Cause or Effect

Lipids are of one of the four basic types of molecules of life and its derivatives serve diverse functions in the body. Generally acclaimed functions of lipids include shock absorption and insulation, and energy storage of the body. Phospholipids and cholesterol form the integral part of cell membrane. In addition cholesterol serves as the precursor for bile salts, male and female sex hormones, vitamin D and adrenocortical hormones. Complex lipids consist of neutral lipid core of cholesterol esters and or triacylglycerol and proteins are the chylomicrons, VLDL, LDL and HDL which serve as the carriers of fats, fatty acids and other lipids in the body. Complex lipids are tightly controlled in the body. Its dysregulation has been mainly linked to obesity, diabetes and insulin resistance though the issue is yet to be clearly understood. The present review evaluates recent reports in this regards and try to explain the relationship between dyspidemia and insulin resistance. DOI: http://dx.doi.org/10.3329/bjmb.v7i1.18576 Bangladesh J Med Biochem 2014; 7(1): 27-31

Phosphatidylethanolamine increases perilipin 2 binding to synthetic lipid droplets (606.5)

Excess lipid is stored in organelles known as lipid droplets. Each lipid droplet is composed of a neutral lipid core surrounded by a phospholipid monolayer. The surface of each lipid droplet is decorated with proteins that facilitate fat storage and utilization. Our lab studies perilipin 2, a protein that binds to the surface of lipid droplets and slows the degradation of stored fat. We aim to understand how the phospholipid composition of the lipid droplet influences perilipin 2 binding. Here, we show that perilipin 2 binding to synthetic lipid droplets is influenced by the phospholipid composition of the surface. Specifically, perilipin 2 binding decreases as phosphatidylcholine (PC) levels decrease relative to phosphatidylethanolamine (PE). This result may influence the progression of alcohol‐induced fatty liver disease. Our experiments show that alcohol consumption in rats not only increases hepatic triacylglyceride storage and lipid droplet accumulation but also alters the phospholipid composition of hepatic lipid droplets. We observe a decrease in the PC:PE ratio of hepatic lipid droplets following alcohol consumption. Future experiments will continue to explore the link between the lipid droplet phospholipid composition, perilipin 2 binding, and alcohol‐induced fatty liver disease.Grant Funding Source: Supported by a grant to St. Olaf College from the Howard Hughes Medical Institute through the Precol

A Novel Octanuclear Vanadium(V) Oxide Cluster Complex Having an Unprecedented Neutral V8O20 Core Functionalized with 4,4′-Di-tert-butyl-2,2′-bipyridine

A novel octanuclear vanadium(V) oxide cluster complex, [V8O20(4,4'-(t)Bubpy)4] (1), was synthesized and characterized by single-crystal X-ray structure analysis to reveal that 1 has an unprecedented neutral V8O20 core. An unexpected interconversion between 1 and the methoxo(oxo)vanadium(V) cluster complex, [V4O8(OMe)4(4,4'-(t)Bubpy)2] (2), was observed upon changes in the solvent systems.

Studying Lipid Interactions of Perilipin 3/ Tip 47 using Phospholipid Monolayers

Lipid droplets are found in all eukaryotes and are considered as dynamic cell organelles. In addition to acting as neutral lipid stores, they are also involved in various biological processes such as membrane formation, cell signaling and hormone synthesis. Many aspects of lipid droplet biogenesis and function are not yet fully understood. The basic structure of a lipid droplet consists of a neutral lipid core of triacylglycerols and cholesterol esters surrounded by a monolayer of phospholipids, free cholesterol and proteins.

Naturally Occurring Follicle-Stimulating Hormone Glycosylation Variants

Follicle-stimulating hormone (FSH) is a member of the glycoprotein hormone family, which is a subfamily of the cystine knot growth factor superfamily [1,2]. The glycoprotein hormones are composed of heterodimeric glycoprotein subunits, a common α-subunit, and a hormone-specific β-subunit. While the α-subunit primary structure is identical for all glycoprotein hormones within the same species, the oligosaccharide populations differ in a hormone-specific manner [3–6]. Characterizing the oligosaccharides released from an α-subunit preparation can identify the hormone from which the subunit was derived [7]. There are 3 to 4 β-subunits in vertebrates, which combine with α-subunit to create either FSH, luteinizing hormone (LH), thyroid-stimulating hormone (TSH), or in primates and equids, chorionic gonadotropin (CG) [8]. As both glycoprotein hormone subunits are cystine knot proteins [9–11] the protein backbone is folded into a series of three loops, two relatively rigid hairpin loops on one side of the knot, designated L1 and L3, and a single, flexible loop on the other side [12], designated L2. Oligosaccharides are attached to all 3 loops in a subunit-specific pattern (Figure 1). FSH subunits possess two potential N-glycosylation sites on each subunit and all four are of the Asn-Xaa-Thr type, which exhibit very efficient carbohydrate attachment [13]. Indeed, the α-subunit is always glycosylated at both sites in all known glycoprotein hormones. Because FSH α and β subunits co-migrate during electrophoresis, it is difficult to detect missing N-glycans in this hormone. FSHβ-specific Western blots have revealed partial glycosylation in equine FSHβ, human FSHβ (hFSH β), rhesus FSH β, and Japanese macaque FSHβ [14–16]. During the past few years, we have studied partially glycosylated hFSH isolated from pituitary extracts, postmenopausal urine, and conditioned tissue culture medium containing recombinant hFSH. Each glycosylation site in hFSH is decorated with a population of N-glycans. When total glycans are removed from reduced, carboxy-methylated FSH subunits, 39–130 glycans are found in mass spectra. We have data from only one glycosylation site, αAsn52, which possessed 29 neutral core ions, and when decorated with various patterns of sialic acid grew to 109 unique glycan structures. Micro heterogeneity can affect electrophoretic mobility, for example, placental hCGα with hybrid and biantennary glycans migrated faster than pituitary hFSHα, with triantennary, biantennary and tetraantennary glycans, which complicated sorting out the hFSH variants that resulted from loss of one or more N-glycans [17].

Transfer of a weakly bound electron in collisions of Rydberg atoms with neutral particles. I. Long-range interaction effects in the ionic-covalent coupling

Ion-pair formation processes are studied in collisions of Rydberg atoms with neutral particles possessing small electron affinities. Nonadiabatic transitions from a Rydberg covalent term to an ionic term of a quasi-molecule are considered using the modified Landau-Zener theory supplemented with calculation of survival factors of an anion decaying in the Coulomb field of a positive ion core. Using the technique of irreducible tensor operators and the momentum representation of the wavefunction of a highly excited atom, exact expressions are obtained for transition matrix elements and the ionic-covalent coupling parameter. The approach developed in the paper provides the description beyond the scope of a conventional assumption about a small variation of the wavefunction of the Rydberg atom on the range of electron coordinates determined by the characteristic radius of the wavefunction of the anion. This allows one to correctly consider long-range effects of the interaction between a weakly bound electron and the neutral core of a negative ion in processes under study. It is shown by the example of thermal collisions of Xe(nf) atoms with CH3CN molecules that this is very important for a reliable quantitative description of anion formation with a low binding energy. The results are compared with experiments and calculations performed within the framework of a number of approximate methods.

Preparation and properties of adsorption material from corn stalks core when used for enzyme immobilization and the subsequent activities of the adsorbed enzymes

This study investigates the characteristics of core adsorption material (CAM) prepared from corn stalks core (Core) by glycol solvent treatment (high pressure boiling at 120°C for 30min using a 50:3 liquor/solid ratio with 2%, w/w sodium hydroxide). The structures of CAM and Core were compared by FT-IR, SEM and XRD. Maltogenic amylase from Aspergillus awamori var., neutral proteins from Source Organism and lipase from Pseudomonas aeruginosa were selected as model enzymes in order to assess their potential applicability for enzyme immobilization. Adsorption characteristics for the different enzymes on CAM were studied and the activity of the immobilized enzymes was evaluated. The results show that CAM has many hydroxyl groups, more flakes, irregular indentations and grooves and a proportionally larger amount of hemi-cellulose than Core, which results in increased numbers of hydroxyl groups in CAM and increased enzyme accessibility into CAM; CAM has the greatest adsorption capacity (9.84±0.32mg/g) for neutral proteins and the best relative activity (total relative activity of 212.6% after being reused three times) after being immobilized, as well as the lowest adsorption capacity (5.15±0.51mg/g) for lipase and the lowest relative activity (total relative activity is 78.23%). The isotherms of maltogenic amylase and neutral proteinase were found to be linear using the Langmuir equation (R2=0.9974 and 0.9966, respectively, p<0.0001) and lipase was found to be linear using the Freundlich equation (R2=0.9331, p<0.0075) in the studied concentration range; CAM could adsorb neutral proteinase and could be used in the simple and inexpensive production of large quantities of pure industrial neutral proteinase and Core can be used to prepare CAM.

Application of flow cytometry for estimation of lipid content changes induced by arachidonic acid and methyl-β-cyclodextrin in the lipid bodies of epithelial cells

Lipid bodies (LB) are dynamic inducible organelles with the key roles in cellular lipid metabolism, intracellular trafficking and signaling. These structures have a neutral lipid-rich core which contains mainly triacylglycerides (TAG) and cholesterol esters (CE). With the use of flow cytometry and lipophylic fluorescent dye Nile red (NR) we studied LB biogenesis in nonfixed freshly isolated epithelial cells derived from the frog (Rana temporaria L.) urinary bladder. These cells are characterized by numerous small LB located diffusely in the cytoplasm. To target neutral lipids in LB, we used arachidonic acid (AA), an inducer of LB biogenesis in different cell types, and methyl-β-cyclodextrin (MβCD), non-permeable cholesterol acceptor, widely used to extract cholesterol from the lipid rafts. The cells were incubated with 10–50 μM AA for 1 h or with 400–2000 μM MβCD for 30 min; after that they were stained with NR, and fluorescence was measured by flow cytometer at λex = 488 nm and λem = 575 ± 15 nm. In parallel, side scatter (SS) was analyzed. It was found that AA in a dose-dependent manner increased NR fluorescence. At a maximal concentration used, AA increased NR fluorescence and SS by 41 ± 2% and by 15 ± 3% (p < 0.001), respectively. Analysis of lipid composition of cell extracts revealed a significant increase of TAG by 10 μM AA. MβCD starting from 400 μM decreased dose-dependently the NR fluorescence and SS. Its effect was accompanied by a decrease of cellular free cholesterol by 6% (p < 0.01) and cholesterol ester by 21% (p < 0.001). This fact indicates mobilization of cholesterol from cholesterol esters stored in LB in order to restore cholesterol level in the plasma membrane. Taken together, our data demonstrate that flow cytometry in combination with NR staining represents a reliable tool to be used for recording of changes in different neutral lipids class content within LB in living cells non-specialized on the fat storage.

Induction of protein conformational change inside the charged electrospray droplet

The behavior of the analyte molecules inside the neutral core of the charged electrospray (ES) droplet is not unambiguously known to date. The possibility of protein conformational change inside the charged ES droplet has been investigated. The ES droplets encapsulating the protein molecules were exposed to the acetic acid vapor in the ionization chamber to absorb the acetic acid vapor. Because of the faster evaporation of water than that of acetic acid, the droplets became enriched with acetic acid and thus altered the solvent environment (e.g. pH and polarity) of the final charged droplets from where the naked charged analytes (proteins) are formed. Thus, the perturbation of the ES droplet solvent environment resulted in the protein conformational change (unfolding) during the short lifespan of the ES droplet and that is reflected by the multimodal charge state distribution in the corresponding mass spectra. Further, the extent of this conformational change inside the ES droplet was found to be related to the structural flexibility of the protein. Although the protein conformational change inside the ES droplet has been driven by using acetic acid vapor in the present study, the results would help in the near future to understand the spontaneity of the conformational change of the analyte on the millisecond timescale of phase transition in the natural way of ES process.

Effect of nanoholes on the vortex core fermion spectrum and heat transport in p-wave superconductors

The spectrum of core excitations of the Abrikosov vortex pinned by a nanohole of the size of the coherence length is considered. While the neutral zero energy Majorana core state remains intact due to its topological origin, the energy of charged excitations is significantly enhanced compared to that in the unpinned vortex. As a consequence of the pinning the minigap separating the Majorana state from the charged levels increases from Δ2/EF (EF is the Fermi energy and Δ is the bulk p-wave superconducting gap) to a significant fraction of Δ. Suppression of the thermodynamic and kinetic effects of the charged excitations allows us to isolate the Majorana state so it can be used for quantum computation. It is proposed that thermal conductivity along the vortex cores is a sensitive method to demonstrate the minigap. Using the Butticker–Landauer–Kopnin formula, we calculate the thermal conductance beyond the linear response as a function of the hole radius.

Periodic Behavior of Lanthanide Coordination within Reverse Micelles

Trends in lanthanide(III) (Ln(III)) coordination were investigated within nanoconfined solvation environments. Ln(III) ions were incorporated into the cores of reverse micelles (RMs) formed with malonamide amphiphiles in n-heptane by contact with aqueous phases containing nitrate and Ln(III); both insert into pre-organized RM units built up of DMDOHEMA (N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide) that are either relatively large and hydrated or small and dry, depending on whether the organic phase is acidic or neutral, respectively. Structural aspects of the Ln(III) complex formation and the RM morphology were obtained by use of XAS (X-ray absorption spectroscopy) and SAXS (small-angle X-ray scattering). The Ln(III) coordination environments were determined through use of L(3)-edge XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure), which provide metrical insights into the chemistry across the period. Hydration numbers for the Eu species were measured using TRLIFS (time-resolved laser-induced fluorescence spectroscopy). The picture that emerges from a system-wide perspective of the Ln-O interatomic distances and number of coordinating oxygen atoms for the extracted complexes of Ln(III) in the first half of the series (i.e., Nd, Eu) is that they are different from those in the second half of the series (i.e., Tb, Yb): the number of coordinating oxygen atoms decrease from 9O for early lanthanides to 8O for the late ones--a trend that is consistent with the effect of the lanthanide contraction. The environment within the RM, altered by either the presence or absence of acid, also had a pronounced influence on the nitrate coordination mode; for example, the larger, more hydrated, acidic RM core favors monodentate coordination, whereas the small, dry, neutral core favors bidentate coordination to Ln(III). These findings show that the coordination chemistry of lanthanides within nanoconfined environments is neither equivalent to the solid nor bulk solution behaviors. Herein we address atomic- and mesoscale phenomena in the under-explored field of lanthanide coordination and periodic behavior within RMs, providing a consilience of fundamental insights into the chemistry of growing importance in technologies as diverse as nanosynthesis and separations science.

Theoretical Study on the Structure and Stabilities of Molecular Clusters of Oxalic Acid with Water

The importance of aerosols to humankind is well-known, playing an integral role in determining Earth's climate and influencing human health. Despite this fact, much remains unknown about the initial events of nucleation. In this work, the molecular properties of common organic atmospheric pollutant oxalic acid and its gas phase interactions with water have been thoroughly examined. Local minima single-point energies for the monomer conformations were calculated at the B3LYP and MP2 level of theory with both 6-311++G(d,p) and aug-cc-pVDZ basis sets and are compared with previous works. Optimized geometries, relative energies, and free energy changes for the stable clusters of oxalic acid conformers with up to six waters were then obtained from B3LYP calculations with 6-31+G(d) and 6-311++G(d,p) basis sets. Initially, cooperative binding is predicted to be the most important factor in nucleation, but as the clusters grow, dipole cancellations are found to play a pivotal role. The clusters of oxalic acid hydrated purely with water tend to produce extremely stable and neutral core systems. Free energies of formation and atmospheric implications are discussed.

Species Differences Drive Nonneutral Structure in Pleistocene Coral Communities

Although ecological assemblages frequently depart from neutral model predictions, these discrepancies have not been unambiguously attributed to neutral theory's core assumption: that community structure is primarily the result of chance variation in birth, death, speciation, and dispersal, rather than the manifestation of demographic differences among species. Using coral communities in Barbados from four time periods during the Pleistocene, we demonstrate that the neutral theory cannot explain coral community similarity distributions, species' regional abundance distributions, or their local occupancy. Furthermore, discrepancies between the neutral theory and the observed communities can be attributed to violation of the core assumption of species equivalence. In particular, species' variable growth rates are driving departures from neutral predictions. Our results reinforce an understanding of reef coral community assembly that invokes trade-offs in species' demographic strategies. The results further suggest that conservation management actions will fail if they are based on the neutral assumption that different coral species are equally able to create live coral cover in the shallow-water reef environment. These findings highlight the importance of developing biodiversity theory that can parsimoniously incorporate species differences in coral reef communities, rather than further elaborating neutral theory.