scholarly journals Electric-field–induced assembly and propulsion of chiral colloidal clusters

2015 ◽  
Vol 112 (20) ◽  
pp. 6307-6312 ◽  
Author(s):  
Fuduo Ma ◽  
Sijia Wang ◽  
David T. Wu ◽  
Ning Wu
Keyword(s):  
Electric Fields ◽  
Soft Matter ◽  
Building Blocks ◽  
Biological Properties ◽  
Model Systems ◽  
Chiral Molecules ◽  
Simple Method ◽  
Out Of Plane ◽  
Cluster Configuration ◽  
Microscale Transport

Chiral molecules with opposite handedness exhibit distinct physical, chemical, or biological properties. They pose challenges as well as opportunities in understanding the phase behavior of soft matter, designing enantioselective catalysts, and manufacturing single-handed pharmaceuticals. Microscopic particles, arranged in a chiral configuration, could also exhibit unusual optical, electric, or magnetic responses. Here we report a simple method to assemble achiral building blocks, i.e., the asymmetric colloidal dimers, into a family of chiral clusters. Under alternating current electric fields, two to four lying dimers associate closely with a central standing dimer and form both right- and left-handed clusters on a conducting substrate. The cluster configuration is primarily determined by the induced dipolar interactions between constituent dimers. Our theoretical model reveals that in-plane dipolar repulsion between petals in the cluster favors the achiral configuration, whereas out-of-plane attraction between the central dimer and surrounding petals favors a chiral arrangement. It is the competition between these two interactions that dictates the final configuration. The theoretical chirality phase diagram is found to be in excellent agreement with experimental observations. We further demonstrate that the broken symmetry in chiral clusters induces an unbalanced electrohydrodynamic flow surrounding them. As a result, they rotate in opposite directions according to their handedness. Both the assembly and propulsion mechanisms revealed here can be potentially applied to other types of asymmetric particles. Such kinds of chiral colloids will be useful for fabricating metamaterials, making model systems for both chiral molecules and active matter, or building propellers for microscale transport.

Neuropharmacological Screening of Chiral and Non-chiral Phthalimide- Containing Compounds in Mice: in vivo and in silico Experiments

2019 ◽  
Vol 15 (1) ◽  
pp. 102-118 ◽  
Author(s):  
Carolina Campos-Rodríguez ◽  
José G. Trujillo-Ferrara ◽  
Ameyali Alvarez-Guerra ◽  
Irán M. Cumbres Vargas ◽  
Roberto I. Cuevas-Hernández ◽  
...  
Keyword(s):  
Locomotor Activity ◽  
In Silico ◽  
Biological Properties ◽  
Chiral Molecules ◽  
Chiral Compounds ◽  
Plus Maze ◽  
In Silico Studies ◽  
The Central Nervous System

Background: Thalidomide, the first synthesized phthalimide, has demonstrated sedative- hypnotic and antiepileptic effects on the central nervous system. N-substituted phthalimides have an interesting chemical structure that confers important biological properties. Objective: Non-chiral (ortho and para bis-isoindoline-1,3-dione, phthaloylglycine) and chiral phthalimides (N-substituted with aspartate or glutamate) were synthesized and the sedative, anxiolytic and anticonvulsant effects were tested. Method: Homology modeling and molecular docking were employed to predict recognition of the analogues by hNMDA and mGlu receptors. The neuropharmacological activity was tested with the open field test and elevated plus maze (EPM). The compounds were tested in mouse models of acute convulsions induced either by pentylenetetrazol (PTZ; 90 mg/kg) or 4-aminopyridine (4-AP; 10 mg/kg). Results: The ortho and para non-chiral compounds at 562.3 and 316 mg/kg, respectively, decreased locomotor activity. Contrarily, the chiral compounds produced excitatory effects. Increased locomotor activity was found with S-TGLU and R-TGLU at 100, 316 and 562.3 mg/kg, and S-TASP at 316 and 562.3 mg/kg. These molecules showed no activity in the EPM test or PTZ model. In the 4-AP model, however, S-TGLU (237.1, 316 and 421.7 mg/kg) as well as S-TASP and R-TASP (316 mg/kg) lowered the convulsive and death rate. Conclusion: The chiral compounds exhibited a non-competitive NMDAR antagonist profile and the non-chiral molecules possessed selective sedative properties. The NMDAR exhibited stereoselectivity for S-TGLU while it is not a preference for the aspartic derivatives. The results appear to be supported by the in silico studies, which evidenced a high affinity of phthalimides for the hNMDAR and mGluR type 1.

LBE for Generalized Hydrodynamics

2018 ◽  
Author(s):  
Sauro Succi
Keyword(s):  
Potential Energy ◽  
Electric Fields ◽  
Chemical Reactions ◽  
Soft Matter ◽  
Fluid Motion ◽  
Life Sciences ◽  
Scientific Discipline ◽  
The Past ◽  
Generalized Hydrodynamics ◽  
Internal Forces

This chapter presents the main techniques to incorporate the effects of external and/or internal forces within the LB formalism. This is a very important task, for it permits us to access a wide body of generalized hydrodynamic applications whereby fluid motion couples to a variety of additional physical aspects, such as gravitational and electric fields, potential energy interactions, chemical reactions and many others. It should be emphasized that while hosting a broader and richer phenomenology than “plain” hydrodynamics, generalized hydrodynamics still fits the hydrodynamic picture of weak departure from suitably generalized local equilibria. This class is all but an academic curiosity; for instance, it is central to the fast-growing science of Soft Matter, a scientific discipline which has received an impressive boost in the past decades, under the drive of micro- and nanotechnological developments and major strides in biology and life sciences at large.

scholarly journals Mechanically axially chiral catenanes and noncanonical mechanically axially chiral rotaxanes

2022 ◽  
Author(s):  
Stephen Goldup ◽  
John Maynard ◽  
Peter Gallagher ◽  
David Lozano ◽  
Patrick Butler
Keyword(s):  
Building Blocks ◽  
Biological Properties ◽  
Mirror Image ◽  
Symmetry Properties ◽  
Covalently Bonded ◽  
Axially Chiral ◽  
Mechanical Bond ◽  
A Chain ◽  
Lord Kelvin ◽  
Molecular Rings

Abstract The term chiral was introduced by Lord Kelvin over a century ago to describe objects that are distinct from their own mirror image. Chirality is relevant in many scientific areas, but particularly chemistry because different mirror image forms of a molecule famously have different biological properties. Chirality typically arises in molecules due to a rigidly chiral arrangement of covalently bonded atoms. Less generally appreciated is that molecular chirality can arise when molecules are threaded through one another to create a mechanical bond. For example, when two molecular rings with chemically distinct faces are joined like links in a chain the resulting structure is chiral even when the rings themselves are not. We re-examined the symmetry properties of such mechanically axially chiral catenanes and in doing so identified a straightforward route to these molecules from simple building blocks. This also led to the discovery of a previously overlooked mechanical stereogenic unit that can arise when such a ring encircles a dumbbell-shaped axle to generate a rotaxane. These insights allowed us to produce the first highly enantioenriched axially chiral catenane and the same approach gave access to a molecule containing the newly identified noncanonical axially chiral rotaxane motif. With methods to access these structures in hand, the process of exploring their properties and applications can now begin.

scholarly journals Transcranial alternating current stimulation entrains single-neuron activity in the primate brain

2019 ◽  
Vol 116 (12) ◽  
pp. 5747-5755 ◽  
Author(s):  
Matthew R. Krause ◽  
Pedro G. Vieira ◽  
Bennett A. Csorba ◽  
Praveen K. Pilly ◽  
Christopher C. Pack
Keyword(s):  
Human Brain ◽  
Electric Fields ◽  
Critical Role ◽  
Spike Timing ◽  
Model Systems ◽  
Neuron Activity ◽  
Transcranial Electrical Stimulation ◽  
Noninvasive Technique ◽  
Early Results ◽  
Wide Range

Spike timing is thought to play a critical role in neural computation and communication. Methods for adjusting spike timing are therefore of great interest to researchers and clinicians alike. Transcranial electrical stimulation (tES) is a noninvasive technique that uses weak electric fields to manipulate brain activity. Early results have suggested that this technique can improve subjects’ behavioral performance on a wide range of tasks and ameliorate some clinical conditions. Nevertheless, considerable skepticism remains about its efficacy, especially because the electric fields reaching the brain during tES are small, whereas the likelihood of indirect effects is large. Our understanding of its effects in humans is largely based on extrapolations from simple model systems and indirect measures of neural activity. As a result, fundamental questions remain about whether and how tES can influence neuronal activity in the human brain. Here, we demonstrate that tES, as typically applied to humans, affects the firing patterns of individual neurons in alert nonhuman primates, which are the best available animal model for the human brain. Specifically, tES consistently influences the timing, but not the rate, of spiking activity within the targeted brain region. Such effects are frequency- and location-specific and can reach deep brain structures; control experiments show that they cannot be explained by sensory stimulation or other indirect influences. These data thus provide a strong mechanistic rationale for the use of tES in humans and will help guide the development of future tES applications.

Ab initio studies on amides: conformational preferences of diacetamide and barriers to interconversion of the conformers

1980 ◽  
Vol 33 (11) ◽  
pp. 2337 ◽  
Author(s):  
L Radom ◽  
NV Riggs
Keyword(s):  
Hydrogen Atom ◽  
Ab Initio ◽  
Internal Rotation ◽  
Model Systems ◽  
Methyl Groups ◽  
Electrostatic Repulsion ◽  
Conformational Preferences ◽  
Out Of Plane ◽  
Model Transition ◽  
Good Agreement

Diacetamide, like other diacylamines, is capable of existing in three basic conformations about the N-C bonds. Optimization (STO-3G) of model systems in which all first-row atoms and the amido hydrogen atom are held coplanar predicts that the E,Z conformer (3) is of lowest energy, the Z,Z conformer (2) of somewhat higher energy (4.2 kJ mol-1), and the E,E conformer (1) of highest energy (23.6 kJ mol-1); 4-31G evaluation of the energies suggests that (1) and (2) are each of higher energy than (3) by 27-28 kJ mol-1. It is suggested that (2) is destabilized with respect to (3) by electrostatic repulsion of the two negatively charged oxygen atoms whereas destabilization of (1) is due to substantial methyl-methyl steric interactions as reflected in the very wide <CNC (136°); the energy of (1) is, however, raised by out-of-plane or rotational movements of the methyl groups, i.e., the preferred structure (excluding methyl hydrogens) is planar. The calculated height of the barrier to internal rotation of (3) by either of two model transition states is 41-45 kJ mol-1, in good agreement with an experimental value of 45.2 kJ mol-1 in solution at -60°.

Metallic Nanowires From Carbon Nanotube Building Blocks: The Effect of Atomic Defects on the Nanotube Influencing Nanowire Growth

2003 ◽  
Author(s):  
B. Panchapakesan ◽  
Kousik Sivakumar ◽  
Shaoxin Lu
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Electric Field ◽  
Building Blocks ◽  
Model Systems ◽  
Initial Surface ◽  
Sensors And Actuators ◽  
Platinum Nanowires ◽  
Defect Sites ◽  
Current Densities

Manipulation and control of matter at the nano- and atomic level are crucial for the success of nano-scale sensors and actuators. The ability to control and synthesize multilayer structures using carbon nanotubes that will enable to build electronic devices within a nanotube is still in its infancy. In this paper, we present results on selective electric field assisted deposition of metals on carbon nanotubes realizing metallic nanowire structures. Silver and platinum nanowires has been fabricated using this approach due to its applications in chemical sensing sensing as catalytic materials to sniff toxic agents and in the area of biomedical nanotechnology for construction of artificial muscles. The electric field assisted technique allows the deposition of metals with high degree of selectivity on carbon nanotubes by manipulating the charges on the surface of the nanotubes. The thickness and the growth of the nanowires was altered by inducing defects on the initial surface of the nanotubes that affected the local current densities and electrochemical reduction of silver and platinum on those defect sites. SEM and TEM investigations revealed silver and platinum nanowires between 10 nm-100 nm in diameter. Relatively higher metal deposition was achieved in defect related sites or places where the nanotubes criss-crossed each other, due to the high current densities in these sites. The present technique is versatile and enables the fabrication of host of different types of metallic and semiconduting nanowires using carbon nanotube templates for nanoelectronics and myriad of sensor applications. Further, nanowires can also serve as model systems for studying quantum size effects in these dimensions.

scholarly journals The Generated Databases (GDBs) as a Source of 3D-shaped Building Blocks for Use in Medicinal Chemistry and Drug Discovery

2020 ◽  
Vol 74 (4) ◽  
pp. 241-246 ◽  
Author(s):  
Kris Meier ◽  
Sven Bühlmann ◽  
Josep Arús-Pous ◽  
Jean-Louis Reymond
Keyword(s):  
Drug Discovery ◽  
Medicinal Chemistry ◽  
Organic Molecules ◽  
Chemical Space ◽  
Building Blocks ◽  
Chiral Molecules ◽  
Hydrogen Atoms ◽  
Quaternary Centers ◽  
Medical Needs ◽  
Unmet Medical Needs

Drug discovery is in constant need of new molecules to develop drugs addressing unmet medical needs. To assess the chemical space available for drug design, our group investigates the generated databases (GDBs) listing all possible organic molecules up to a defined size, the largest of which is GDB-17 featuring 166.4 billion molecules up to 17 non-hydrogen atoms. While known drugs and bioactive compounds are mostly aromatic and planar, the GDBs contain a plethora of non-aromatic 3D-shaped molecules, which are very useful for drug discovery since they generally have more desirable absorption, distribution, metabolism, excretion and toxicity (ADMET) properties. Here we review GDB enumeration methods and the selection and synthesis of GDB molecules as modulators of ion channels. We summarize the constitution of GDB subsets focusing on fragments (FDB17), medicinal chemistry (GDBMedChem) and ChEMBL-like molecules (GDBChEMBL), and the ring system database GDB4c as a rich source of novel 3D-shaped chiral molecules containing quaternary centers, such as the recently reported trinorbornane.

Recent Advances in the Synthesis of Enantiomerically Enriched Diaryl, Aryl Heteroaryl, and Diheteroaryl Alcohols through Addition of Organometallic Reagents to Carbonyl Compounds

Synthesis ◽  
2020 ◽  
Vol 52 (13) ◽  
pp. 1855-1873
Author(s):  
Senthil Narayanaperumal ◽  
Ricardo S. Schwab ◽  
Wystan K. O. Teixeira ◽  
Danilo Yano de Albuquerque
Keyword(s):  
Carbonyl Compounds ◽  
Building Blocks ◽  
Short Review ◽  
Biological Properties ◽  
Enantioselective Synthesis ◽  
Grignard Reagents ◽  
Organometallic Reagents ◽  
Important Family ◽  
Organolithium Reagents ◽  
Organozinc Reagents

Enantiomerically enriched diaryl, aryl heteroaryl, and dihetero­aryl alcohols are an important family of compounds known for their biological properties. Moreover, these molecules are highly privileged scaffolds used as building blocks for the synthesis of pharmaceutically relevant products. This short review provides background on the enantioselective arylation and heteroarylation of carbonyl compounds, as well as, the most significant improvements in this field with special emphasis on the application of organometallic reagents.1 Introduction2 Background on the Enantioselective Synthesis of Diaryl, Aryl Heteroaryl, and Diheteroaryl Alcohols3 Organozinc Reagents4 Organolithium Reagents5 Grignard Reagents6 Organoaluminum Reagents7 Organotitanium Reagents8 Organobismuth Reagents9 Miscellaneous10 Conclusion

scholarly journals Statistics of Joule heating in the auroral zone and polar cap using Astrid-2 satellite Poynting flux

2004 ◽  
Vol 22 (12) ◽  
pp. 4133-4142 ◽  
Author(s):  
A. Olsson ◽  
P. Janhunen ◽  
T. Karlsson ◽  
N. Ivchenko ◽  
L. G. Blomberg
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Joule Heating ◽  
Building Blocks ◽  
Auroral Zone ◽  
Power Budget ◽  
Flux Method ◽  
Poynting Flux ◽  
Background Magnetic Field ◽  
Magnetospheric Configuration And Dynamics

Abstract. We make a statistical study of ionospheric Joule heating with the Poynting flux method using six months of Astrid-2/EMMA electric and magnetic field data during 1999 (solar maximum year). For the background magnetic field we use the IGRF model. Our results are in agreement with earlier statistical satellite studies using both the ΣPE2 method and the Poynting flux method. We present a rather comprehensive set of fitted Joule heating formulas expressing the Joule heating in given magnetic local time (MLT) and invariant latitude (ILAT) range under given solar illumination conditions as a function of the Kp index, the AE index, the Akasofu epsilon parameter and the solar wind kinetic energy flux. The study thus provides improved and more detailed estimates of the statistical Joule heating. Such estimates are necessary building blocks for future quantitative studies of the power budget in the magnetosphere and in the nightside auroral region. Key words. Ionosphere (electric fields and currents; ionosphere-magnetosphere interactions) – Magnetospheric physics (magnetospheric configuration and dynamics)

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