Spherical Molecules Research Articles

An Adamantane Capsule and its Efficient Uptake of Spherical Guests up to 3 nm in Water.

Efficient uptake of small to large guests, with a large difference in relative size, is quite rare for synthetic host compounds. Herein we designed and prepared a micellar capsule, composed of bent amphiphiles bearing two adamantyl groups, as a new host with a well-defined nanostructure. Unlike previous covalent, coordination, and hydrogen-bonding hosts, the adamantane-based capsule displays unusual uptake abilities toward spherical molecules with small (∼0.6 nm in diameter; e.g., adamantane) to medium size (∼1 nm; e.g., fullerene) as well as large size (∼3 nm; i.e., metal-organic polyhedra (MOP)), where the size differences are up to 5-fold, in water. Moreover, the resultant MOP-uptaking capsule incorporates medium-sized molecules (e.g., perylene and eosin Y) into the polyhedral cavity to generate ternary core-shell structures.

Investigation of the Physical and Chemical Characteristics of the Zeolites of the Kholinsky Deposit

Introduction. The mineral resource base of Russia has effective sorption substances that meet pharmaceutical requirements. Promising mineral raw materials are Zeolites, which combine the properties of an adsorbent and a "molecular sieve" due to the porous structure. In addition to the enterosorption direction, natural Zeolites are a source of macro-and microelements, which determines their use as biologically active food additives.Aim. Study of the physical and chemical characteristics of the Zeolites of the Kholinsky deposit.Materials and methods. The zeolite mineral raw materials of the Kholinsky deposit were used as objects of research. Optical microscopy was performed using a Leica DM direct microscope (Microsystems, Germany). Energy dispersion analysis was performed using an electron scanning microscope JSM-5300 (Jeol Ltd, Japan). The sorption characteristics were studied using the ASAP 2400 device (Micromeritics, USA) according to the method. The construction of a virtual three-dimensional molecular model of the Zeolite was carried out using the program Java Applet Jmol.Results and discussion. The physicochemical properties of Zeolites are investigated. It is established that morphologically the particles of the zeolite phase have a size of 5-30 microns, they are evenly distributed over the entire area of the site and represent the first structural level. Particles of the zeolite phase with a size of 5-6 microns form the second structural level due to Clinoptilolite crystals, microcracks and microgeodes. Based on the energy-dispersion spectral analysis, an increased content of the elements K, Na was revealed, which indicates the alkaline composition of the cation exchange complex. The studied Zeolite samples have micropores (volume 0.0031 cm3/g), mesopores (volume 0.0675 cm3/g), and a specific surface area of 29.1840 m2/g. A virtual three-dimensional molecular model of the Zeolite of the Kholinsky deposit has been developed. According to the molecular model, the sorption characteristics of the Kholinsky deposit Zeolite were: specific surface area - 1096.31 m2/g (1916.34 m2/cm3), the average diameter of the spherical molecule for adsorption in the pores is 5.97 A.Conclusion. The analysis of the sorption characteristics of the Zeolite revealed the following features: the pores occupy half the volume of the entire Zeolite, which are available for the sorption of water and low-molecular substances. Each pore in three mutually perpendicular directions communicates with the neighboring ones through "windows". A system of intracrystalline pores and cavities is formed, in which the occlusion and adsorption of molecules of the appropriate size easily occurs.

A Simple Equation for the Free Energy of Liquids.

A simple, three-parameter equation is proposed for the free energy of classical fluids composed of molecules which are not hydrogen bonded. Agreement with experiment is much the same as has been obtained from more complicated three-parameter equations. For spherical and nearly spherical molecules, semiquantitative relations between intermolecular pair potential parameters and the parameters of the proposed equation were found. For alkanes, relations between the parameters and carbon number were noted. These relationships contribute to the understanding of fluid state properties in terms of the properties of the molecules of which they are composed.

Drone–drone collisions over New York City via the kinetic theory of gases

It is anticipated that future skies over urban areas will be busy with drones flying back and forth delivering packages. Taking New York City as an extreme example, it is estimated that by 2026, 2600 delivery drones could simultaneously populate the city's airspace. The drone–drone collision rate of “dumb” drones can be calculated by treating them as a gas of large, randomly moving, spherical molecules, using the kinetic theory of gases. Collisions can be avoided by making each drone “smart,” i.e., by giving each a “sense and avoid” capability for detecting and avoiding a potential collision. For smart drones over New York City, the rate of potential collisions, or encounter rate, extends over a surprisingly large range: from 1 to 170,000 encounters/day, depending on input assumptions. This places stringent constraints on the probability that a smart drone encounter will result in a collision, constraints that must be met by the drone operator. Policy implications are discussed.

On symmetry breaking of dual polyhedra of non-crystallographic group H3.

The study of the polyhedra described in this paper is relevant to the icosahedral symmetry in the assembly of various spherical molecules, biomolecules and viruses. A symmetry-breaking mechanism is applied to the family of polytopes {\cal V}_{H_{3}}(\lambda) constructed for each type of dominant point λ. Here a polytope {\cal V}_{H_{3}}(\lambda) is considered as a dual of a {\cal D}_{H_{3}}(\lambda) polytope obtained from the action of the Coxeter group H3 on a single point \lambda\in{\bb R}^{3}. The H3 symmetry is reduced to the symmetry of its two-dimensional subgroups H2, A1 × A1 and A2 that are used to examine the geometric structure of {\cal V}_{H_{3}}(\lambda) polytopes. The latter is presented as a stack of parallel circular/polygonal orbits known as the `pancake' structure of a polytope. Inserting more orbits into an orbit decomposition results in the extension of the {\cal V}_{H_{3}}(\lambda) structure into various nanotubes. Moreover, since a {\cal V}_{H_{3}}(\lambda) polytope may contain the orbits obtained by the action of H3 on the seed points (a, 0, 0), (0, b, 0) and (0, 0, c) within its structure, the stellations of flat-faced {\cal V}_{H_{3}}(\lambda) polytopes are constructed whenever the radii of such orbits are appropriately scaled. Finally, since the fullerene C20 has the dodecahedral structure of {\cal V}_{H_{3}}(a,0,0), the construction of the smallest fullerenes C24, C26, C28, C30 together with the nanotubes C20+6N, C20+10N is presented.

Liposome: A Novel Drug Delivery System

Liposome is a spherical sac phospholipid molecule. It encloses a water droplet especially as form artificially to carry drug into tissue membrane. It is spherical sac vesicle it consists at least one lipid bilayer. Liposomes are mainly development for drug delivery size and size distribution. The process of sonication (extrusion) is required to obtain small size and narrow size distribution of liposome. The main significant role in formulating of potent drug, improve therapeutic effect. Liposome formulation is mainly design in increasing accumulation at the target site, and then resulting effect is targeted to reduce toxicity. There is various method for liposome formulation depending upon lipid drug interaction liposome disposition mechanism- parameters particle size, charge and surface hydration. Liposome is a nanoparticle (size-100nm). Nanoscale drug delivery system using liposome as well as nanoparticle. This technology is for "Rational delivery of chemotherapeutic" drug treatment of cancer. Liposome is use as to study the cell membrane and cell organelles. The advantages of liposome formation using microfluidic approach for bulk-mixing approaches are discussed. Keywords: liposome, lipid bilayer, sonication, nanoparticles, particle size, toxicity.

The Significant Role of the Microfilament System in Tumors.

Actin is the structural protein of microfilaments, and it usually exists in two forms: monomer and polymer. Among them, monomer actin is a spherical molecule composed of a polypeptide chain, also known as spherical actin. The function of actin polymers is to produce actin filaments, so it is also called fibroactin. The actin cytoskeleton is considered to be an important subcellular filament system. It interacts with numerous relevant proteins and regulatory cells, regulating basic functions, from cell division and muscle contraction to cell movement and ensuring tissue integrity. The dynamic reorganization of the actin cytoskeleton has immense influence on the progression and metastasis of cancer as well. This paper explores the significance of the microfilament network, the dynamic changes of its structure and function in the presence of a tumor, the formation process around the actin system, and the relevant proteins that may be target molecules for anticancer drugs so as to provide support and reference for interlinked cancer treatment research in the future.

Global Analysis of 24 Rovibrational Bands of the Octad of the 76GeH4 Molecule

A global fitting method has been developed for spherical top molecules. The octad of the GeH4 molecule comprising 24 interacting states has been investigated. By solving the inverse spectroscopic problem, positions of the band centers and rotational and resonant parameters are calculated. A total of 70 variable parameters allow 1184 initial experimental rovibrational energies to be reproduced with a standard deviation of 1.2·10–3 cm–1.

Molecular-Shape-Dominated Crystal Packing Features of Energetic Materials

Molecular shape is observed to greatly determine the properties of energetic materials (EMs); that is, the spherical molecules generally have high energy while the planar molecules have low sensiti...

Bimolecular Binding Rates for Pairs of Spherical Molecules with Small Binding Sites

Related DatabasesWeb of Science You must be logged in with an active subscription to view this.Article DataHistorySubmitted: 27 February 2020Accepted: 03 November 2020Published online: 20 January 2021Keywordspatchy particles, binding rates, singular perturbations, Berg--Purcell, Brownian motionAMS Subject Headings35B25, 35C20, 35J05, 92C05, 92C40Publication DataISSN (print): 1540-3459ISSN (online): 1540-3467Publisher: Society for Industrial and Applied MathematicsCODEN: mmsubt

In Ukrainian

The regularities of the formation of nanostructures during the evaporation of graphite by the electric ARC – method are studied. Described physicochemical processes in the synthesis reactor . At plasma temperatures taking into account the behavior of particles in electromagnetic fields with extreme temperature and pressure grants. A sequence of organization of matter in the process of forming a structure according to nano-dimensional characteristics is proposed. The self-organization of systems during electric arc evaporation of graphite or graphite-containing electrodes has been studied. The mechanisms of formation of soluble (fullerenes and fullerene-like structures) and insoluble (nanocomposites, CNTs, graphenes) carbon nanostructures are considered. The processes occurring in the electric arc synthesis reactor are analyzed: the process of distribution of charged particles in an electric arc at different times; processes taking place at the anode; the mechanism of carbon vapor formation during graphite evaporation; processes in the gas phase and on the walls of the reactor under the conditions of an electric arc discharge; model of the reactor space zones; formation of carbon nanostructures in the gas phase and on the inner surface of the reactor. use of doped electrodes and metal inserts (sleeves) as catalysts for the synthesis of carbon nanostructures. The sequence of processes in the formation of spherical carbon molecules is studied, and the processes and structural transformations are considered. In the research work, the products (fullerenes and fullerene-like structures, nanocomposites, VNT, graphenes) of electric arc synthesis are presented, and modern methods of analysis are used for their fixation and identification.

Encapsulated virgin coconut oil as a nanoscale in vitro solution against multiple drug resistant Staphylococcus aureus

Niosomes are excellent nanoscale vehicular systems that can carry a variety of drugs and (bioactive) compounds entrapped inside them. Virgin coconut oil (VCO) is the finest grade of coconut oil that is highly enriched with phenolic content, antioxidant activity and also comprises medium chain triglycerides. In this work, niosomes were encapsulated with VCO synthesized by a simple chemical method. The electron microscopy confirmed that spherical nanostructured lipid carrier molecules with a diameter in the range of 180–190 nm were produced. A zeta potential value of −42 mV was a testimony that these nanovehicles were having good stability. The natural oil loaded nanocarrier spheres proved to be potent antibacterial nano-antibiotics against multiple drug resistant (MDR) bacteria. The antibacterial activity of these magic nano-spheres was found to be better than ZnO (metallic oxides) nanoparticles. The nano-antibiotics resulted in 17, 14 and 12 mm zones of inhibition against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant S. aureus (VRSA) and a (general) MDR strain of S. aureus in contrast to nanoparticles that resulted in zones of inhibitions 7, 8 and 6 mm for the same bacterial strains. Niosomes prove to be an excellent nanocarrier system that can encapsulate a number of bio-active compounds.

Catalytic enantioselective synthesis of chiral tetraarylmethanes

While synthetic chemistry has experienced substantial development in the past century, challenges still remain to fully satisfy the needs in drug development. A bias in sampling linear and disc-shaped molecules in drug discovery over spherical ones has existed due to the lack of efficient access to the latter chemical space. Specifically, efficient strategies to synthesize tetraarylmethanes, a unique family of spherical molecules, has remained scarce. In particular, there has been essentially no efficient asymmetric synthesis of chiral tetraarylmethanes due to the overwhelming steric congestion and challenging stereocontrol encountered in assembly of the all-aryl-substituted quaternary stereocentre. Here we disclose an efficient catalytic synthesis of chiral tetraarylmethanes with high enantioselectivity via a stereoconvergent formal nucleophilic substitution reaction. Control experiments and density functional theory calculations provided strong support on hydrogen bonding interactions as the key elements to successful stereocontrol. The obtained enantioenriched products showed impressive preliminary anticancer activities. Tetraarylmethanes display special properties due to their spherical nature and are applied in various areas, but strategies for their asymmetric production are lacking. Now, their enantioselective synthesis is reported and in vitro studies indicate their potential as anticancer agents.

Influence of Ionic Strength on Hydrophobic Interactions in Water: Dependence on Solute Size and Shape.

Hydrophobicity is a phenomenon of great importance in biology, chemistry, and biochemistry. It is defined as the interaction between nonpolar molecules or groups in water and their low solubility. Hydrophobic interactions affect many processes in water, for example, complexation, surfactant aggregation, and coagulation. These interactions play a pivotal role in the formation and stability of proteins or biological membranes. In the present study, we assessed the effect of ionic strength, solute size, and shape on hydrophobic interactions between pairs of nonpolar particles. Pairs of methane, neopentane, adamantane, fullerene, ethane, propane, butane, hexane, octane, and decane were simulated by molecular dynamics in AMBER 16.0 force field. As a solvent, TIP3P and TIP4PEW water models were used. Potential of mean force (PMF) plots of these dimers were determined at four values of ionic strength, 0, 0.04, 0.08, and 0.40 mol/dm3, to observe its impact on hydrophobic interactions. The characteristic shape of PMFs with three extrema (contact minimum, solvent-separated minimum, and desolvation maximum) was observed for most of the compounds for hydrophobic interactions. Ionic strength affected hydrophobic interactions. We observed a tendency to deepen contact minima with an increase in ionic strength value in the case of spherical and spheroidal molecules. Additionally, two-dimensional distribution functions describing water density and average number of hydrogen bonds between water molecules were calculated in both water models for adamantane and hexane. It was observed that the density of water did not significantly change with the increase in ionic strength, but the average number of hydrogen bonds changed. The latter tendency strongly depends on the water model used for simulations.

Computation of Fission Product Condensation on Chainlike Aerosols and Agglomerates—II: Role of Energy and Mass Dependence of Molecules

Although aerosols in some postaccident nuclear environments can be nonspherical, chainlike, or agglomerates, there have been limited investigations of the rate processes (such as coagulation, evaporation, condensation, and deposition) involving such particles. In a previous investigation, the understandings of condensation and evaporation on such particles were expanded through use of a one-speed approximation for modeling vapor (or fission product) molecular transport, and the present paper extends that work to energy- and mass-dependent transport of vapor molecules within the context of the linear Boltzmann equation via the Monte Carlo particle transport method for rigid sphere molecules. The results are benchmarked against available numerical results and experimental data for a single sphere, and it is found again that the normalized condensation rate has only a weak dependence on the molecular mass ratio (vapor to background) and that the one-speed approximation is quite good. Results are reported for a range of chainlike and agglomerate aerosols.

Strong optical force of a molecule enabled by the plasmonic nanogap hot spot in a tip-enhanced Raman spectroscopy system

Tip-enhanced Raman spectroscopy (TERS) offers a powerful means to enhance the Raman scattering signal of a molecule as the localized surface plasmonic resonance will induce a significant local electric field enhancement in the nanoscale hot spot located within the nanogap of the TERS system. In this work, we theoretically show that this nanoscale hot spot can also serve as powerful optical tweezers to tightly trap a molecule. We calculate and analyze the local electric field and field gradient distribution of this nanogap plasmon hot spot. Due to the highly localized electric field, a three-dimensional optical trap can form at the hot spot. Moreover, the optical energy density and optical force acting on a molecule can be greatly enhanced to a level far exceeding the conventional single laser beam optical tweezers. Calculations show that for a single H 2 TBPP organic molecule, which is modeled as a spherical molecule with a radius of r m = 1 nm , a dielectric coefficient ε = 3 , and a polarizability α = 4.5 × 10 − 38 C · m 2 / V , the stiffness of the hot-spot trap can reach a high value of about 2 pN / [ ( W / cm 2 ) · m ] and 40 pN / [ ( W / cm 2 ) · m ] in the direction perpendicular and parallel to the TERS tip axis, which is far larger than the stiffness of single-beam tweezers, ∼ 0.4 pN / [ ( W / cm 2 ) · m ] . This hard-stiffness will enable the molecules to be stably captured in the plasmon hot spot. Our results indicate that TERS can become a promising tool of optical tweezers for trapping a microscopic object like molecules while implementing Raman spectroscopic imaging and analysis at the same time.

Molecular size and shape effects: Rotational diffusion and the Stokes-Einstein-Debye relation

Formulation of rotational diffusion coefficient and the Stokes-Einstein-Debye (SED) relation is presented for diatomic molecular liquids by molecular dynamics simulation with two-center Lennard-Jones (2CLJ) potentials. Shear viscosity ηsv and rotational diffusion coefficient Dr are expressed as a function of molecular mass and number density N/V, or moment of inertia, packing fraction, temperature T, interaction energy, and molecular elongation l∗ ≡ l/σ, where N is the number of molecules included in the system volume V, l the bond length in the diatomic molecules, and σ the size parameter used in the LJ potentials. The packing fraction and elongation are the variables expressing molecular size and shape, respectively. These results produce directly a molecular-basis SED relation as Drηsv/T ∝ vm∗1/3l∗−3(N/V), where vm∗ is the dimensionless molecular volume expressed as an analytical function only of elongation l∗. That is, this SED equation depends not on the size but on the shape. This is highly contrasted with the original SED relation based on the size, which suggests overall reconsideration of the relation on a molecular scale. The shape term accounts for a paradox that more spherical molecules such as N2 deviate more strongly from the original SED equation based on a spherical particle. In addition, the SED relation without the size is consistent with the Stokes-Einstein relation for both the Lennard-Jones and 2CLJ liquids expressed as Dηsv/T ∝ (N/V)1/3, where D is the translational self-diffusion coefficient.

The Influence of Electrolyte Solutions on the Mechanical Properties of Bacterial Cellulose

The mechanical characteristics of bacterial cellulose (one of the most promising cellulose-based nanomaterials) fundamentally depend on its moisture content. It has been found that the effect of aqueous solutions of alkali metal chlorides on its strength and deformation properties is determined by the mobility of water molecules in the near coordination spheres of cation hydration shells.

Two Nanometer-Sized High-Nuclearity Homometallic Bromide Clusters (M26Br38)12- (M = Cu, Ag): Syntheses, Crystal Structures, and Efficient Adsorption Properties.

The spontaneous formation of discrete spherical nanosized molecules is ubiquitous in nature; however, the actual structural imitation of such high-symmetry polyhedra from the edge sharing of regular polygons has still proved to be elusive. Herein, two high-nuclearity metal clusters, namely (TTB)4·M26Br38 (M = Cu (1), Ag (2), TTB·Br3 = 1, 3, 5-tris(triethylammoniomethyl)benzene tribromide), have been rationally and solvothermally synthesized and structurally characterized. Single-crystal X-ray analysis confirmed that 1 has I4̅3m symmetry with a (Cu25Br34)12- anion shell enwrapping a CuBr4 tetrahedron and 2 has I4̅3m symmetry with a [Ag26Br34]12- anion shell enwrapping a Br4 pyramid. The diffuse-reflectance UV-vis measurements showed that both compounds possess proper semiconductor behaviors with tunable band gaps of 1.87 eV for 1 and 1.90 eV for 2. Interestingly, all the samples feature distinct adsorption speed and compound 1 shows good adsorption activity for methyl orange (MO) under the same reaction conditions. The effects of pH, temperature, and cyclicity on dye adsorption, together with the thermal stabilities and luminescence properties of the compounds, were also studied. From the cyclic adsorption of compound 1 to the anionic dye MO, it was found that the adsorption of MO was good over three cycles, and the third adsorption rate was still 93.90%.

The New “Noble Gas” Molecule: A Molecular Trip beyond Atoms

In a recent issue of Nature Chemistry, Jishan Wu and co-workers reported the hexacation species of a 3D conjugated molecular cage whose 50 π-electrons follow Hirsch’s rule of 3D aromaticity. We show how Hirsch’s rule connects hydrogenoid atoms, the (unprepared) decacation of the C60 fullerene, and the Wu group’s hexacation.