Evaluation of anchorage loss after en masse retraction in orthodontic patients with maxillary protrusion using friction vs frictionless mechanics: randomized clinical trial.

Objectives: To evaluate anchorage loss after en masse retraction in bimaxillary dentoalveolar protrusion patients using friction vs frictionless mechanics.

Materials And Methods: Thirty patients with bimaxillary dentoalveolar protrusion needing extraction of upper first premolars and en masse retraction with maximum anchorage were included in this two-arm, parallel, single-center, single-blinded randomized clinical trial with a 1:1 allocation ratio using fully sealed opaque envelopes. Friction group retraction utilized elastomeric power chain between miniscrews and hooks crimped mesial to upper canines on 17 × 25 stainless steel archwire.

Outcomes of Head and Neck Neurogenic Tumors.

Background: Lateral neck mass management frequently challenges surgeons. Nerve tissue neoplasms are an uncommon cause of such nodules. Neurogenic tumors form a tiny percentage of the head and neck neoplastic lesions.

Polyhedral Ferraboranes with Iron Carbonyl Vertices: Carbonyl Migration Processes in the Iron Tetracarbonyl Derivatives.

The structures and energetics of the neutral BHFe() ( = 4, 3) and the dianions [BHFe(CO)] ( = 6-14) have been investigated by density functional theory. The low-energy structures of the tricarbonyl dianions [BHFe(CO)] are all found to have deltahedral structures in accordance with their 2+2 skeletal electrons. The low-energy structures of the neutral tricarbonyls BHFe(CO) ( = 6-14) with only 2 skeletal electrons are based on capped (-1)-vertex deltahedra ( = 6, 7, 8) or deltahedra with a degree 6 vertex for the iron atom.

Polyhedral Dicobaltadithiaboranes and Dicobaltdiselenaboranes as Examples of Bimetallic Structures without Bridging Hydrogens.

The geometries and energetics of the -vertex polyhedral dicobaltadithiaboranes and dicobaltadiselenaboranes CpCoEBH (E = S, Se; = 8 to 12) have been investigated via the density functional theory. Most of the lowest-energy structures in these systems are generated from the ( + 1)-vertex most spherical deltahedra by removal of a single vertex, leading to a tetragonal, pentagonal, or hexagonal face depending on the degree of the vertex removed. In all of these low-energy structures, the chalcogen atoms are located at the vertices of the non-triangular face.

Aromaticity in P allotropes and (CH) analogues: significance of their 40 valence electrons?

The currently unknown phosphorus allotrope P is of interest since its 40 total valence electrons is a "magic number" corresponding to a filled 1S1P1D1S1F2P shell such as found in the relatively stable main group element clusters Al and Ge. However, P still remains as an elusive structure not realized experimentally. The lowest energy P structure by a margin of ∼9 kcal mol is shown by density functional theory to be a cuneane analogue with no PP double bonds and two each of P, P, and P rings.

Conventional peritoneal cytology lacks the prognostic significance of detecting local or peritoneal recurrence in colorectal cancer: An Egyptian experience.

Background And Aim: Colorectal cancer (CRC) accounts for over 8% of all deaths each year, with 1.2 million new cases diagnosed annually worldwide. It represents the seventh most common cancer in Egypt.

Enhancement of Ion Pairing of Sr(II) and Ba(II) Salts by a Tritopic Ion-Pair Receptor in Solution.

Tritopic ion-pair receptors can bind bivalent salts in solution; yet, these salts have a tendency to form ion-pairs even in the absence of receptors. The extent to which such receptors can enhance ion pairing has however remained elusive. Here, we study ion pairing of M (Ba , Sr ) and X (I , ClO ) in acetonitrile with and without a dichlorooxacalix[2]arene[2]triazine-related receptor containing a pentaethylene-glycol moiety.

Correction: Pseudo electron-deficient organometallics: limited reactivity towards electron-donating ligands.

Correction for 'Pseudo electron-deficient organometallics: limited reactivity towards electron-donating ligands' by Anaïs Pitto-Barry et al., Dalton Trans., 2017, 46, 15676-15683.

Nonsphericity in diferratetracarbaboranes having 2n + 2 Wadean skeletal electrons: deviations from closo deltahedral geometries and high-energy kinetically stable isomers.

The diferratetracarbaboranes Cp2Fe2C4Bn-6Hn-2 (n = 10 to 14; Cp = η5-C5H5) as well as the experimentally known C-tetramethyl derivatives Cp2Fe2C4Me4B8H8 have been studied by density functional theory methods. For the Cp2Fe2C4Me4B8H8 system, the three structurally characterized isomers produced under relatively mild conditions having an "open" tetragonal or pentagonal face correspond to the lowest energy structures not based on the 14-vertex closo deltahedron, namely the bicapped hexagonal antiprism. These structures provide examples of kinetically favored but thermodynamically disfavored high-energy metallacarborane structures.

Neutral Rhenadicarbaboranes with Re(CO)(NO) Vertices: A Theoretical Study of Building Blocks for Rhenacarborane-Based Drug Delivery Agents.

The rhenadicarbaborane carbonyl nitrosyls (CBH)Re(CO)(NO), ( = 8 to 12), of interest in drug delivery agents based on the experimentally known CBHRe(CO)(NO) and related species, have been investigated by density functional theory. The lowest energy structures of these rhenadicarbaboranes are all found to have central ReCB most spherical deltahedra in accord with their 2 + 2 Wadean skeletal electrons. Carbon atoms are found to be located preferentially at degree 4 vertices in such structures.

The tetracapped truncated tetrahedron in 16-vertex tetrametallaborane structures: spherical aromaticity with an isocloso rather than a closo skeletal electron count.

Density functional theory studies on the experimentally known Cp*3Rh3B12H12Rh(B4H9RhCp*) as well as the model compounds Cp4Rh4B12H12 and Cp3Rh3B12H12Rh(η3-C3H5) indicate low energy structures with central Rh4B12 tetracapped tetratruncated tetrahedra (TTT) for these 32 Wadean skeletal electron systems. This skeletal electron count corresponds to 2k2 (k = 4) skeletal electrons suggesting a spherical aromatic system with filled 1s + 1p + 1d + 1f molecular orbitals as well as an isocloso 2n (= 32 for n = 16) skeletal electron count. Similar TTT structures are found for the valence isoelectronic 32 skeletal electron systems [Cp4M''4B12H12]4+ (M'' = Ni, Pd, Pt) and [Cp4M'4B12H12]4- (M' = Fe, Ru, Os).

Cationic gold clusters with eight valence electrons: possible spherical aromatic systems with Sigma holes.

The energetically preferred structures of the gold clusters Au9+, Au113+, and Au124+ with eight skeletal electrons have been studied by density functional theory for comparison with the 8-electron Au102+ cluster shown previously to have a highly favored Td tetracapped octahedral structure. The low-energy structures for the Au9+ and Au113+ clusters are found to be similar relatively spherical polyhedra. Such systems can be considered to exhibit spherical aromaticity in accord with their filled 1S21P6 shells, their diatropic NICS(0) values ranging from -21.

Versatile coordination behaviour of the chloro-tetrazine-picolylamine ligand: mixed-valence binuclear Cu(i)/Cu(ii) complexes.

The 3-Cl-6-amino-(2'-picolyl)-1,2,4,5-tetrazine ligand HL has been synthesized and structurally characterized. Its versatile coordination behavior has been evidenced through reactions with Cu(Hfac) and Cu(triflate) precursors, which provided mixed-valence bimetallic CuCu complexes [Cu(μ-Cl)(L)] 2 and [Cu(μ-triflate)(L)] 5. Changing the Cu(ii) precursor and the solvent leads to the formation of mononuclear octahedral Cu(ii) complexes [CuCl(HL)]·2CHCN 3 and [Cu(Hfac)(HL)] 4, in which only the amino-pyridine unit is involved in the coordination of the metal center.

Affinity and Effect of Anticancer Drugs on the Redox Reactivity of Hemoglobin.

Hemoglobin's redox reactivity is affected by anticancer drugs of the antitubulin class. Direct binding of these drugs to hemoglobin, with biomedically relevant affinities, is demonstrated. While this interaction is mostly allosteric, in the case of docetaxel, a direct redox reaction is also observed-correlating well with structural differences between the four compounds.

Magnesium(II) d-Gluconate Complexes Relevant to Radioactive Waste Disposals: Metal-Ion-Induced Ligand Deprotonation or Ligand-Promoted Metal-Ion Hydrolysis?

The complexation equilibria between Mg and d-gluconate (Gluc) ions are of particular importance in modeling the chemical speciation in low- and intermediate-level radioactive waste repositories. NMR measurements and potentiometric titrations conducted at 25 °C and 4 M ionic strength revealed the formation of the MgGluc, MgGlucOH, MgGluc(OH), and MgGluc(OH) complexes. The trinuclear species provides indirect evidence for the existence of multinuclear magnesium(II) hydroxido complexes, whose formation was proposed earlier but has not been confirmed yet.

Reversible complexation of ammonia by breaking a manganese-manganese bond in a manganese carbonyl ethylenedithiolate complex: a theoretical study of an unusual type of Lewis acid.

The reaction of Mn(CO)5Br with sodium ethylenedithiolate was reported in 1968 to give a dark red binuclear H2C2S2Mn2(CO)6 complex possessing the unusual property of complexing reversibly with ammonia to give a yellow H2C2S2Mn2(CO)6·NH3 adduct. In order to provide some insight into the nature of this adduct, density functional studies were performed on the H2C2S2Mn2(CO)n (n = 4 to 8) systems as well as their relevant ammonia and trimethylphosphine adducts. These theoretical studies support the structure of H2C2S2Mn2(CO)6 originally suggested 50 years ago involving the binding of the ethylenedithiolate C[double bond, length as m-dash]C double bond as well as the sulfur atoms to the Mn2 unit with a bonding Mn-Mn distance of ∼2.

Catalytic and stoichiometric flavanone oxidation mediated by nonheme oxoiron(iv) complexes as flavone synthase mimics: kinetic, mechanistic and computational studies.

The present study describes the first example of the stoichiometric and catalytic oxidation of flavanone by synthetic nonheme oxoiron(iv) complexes and their precursor iron(ii) complexes with m-CPBA as the terminal oxidant. These models, including detailed kinetic, mechanistic and computational studies, may serve as the biomimics of flavone synthase (FS) enzymes.

The acidity and self-catalyzed lactonization of l-gulonic acid: Thermodynamic, kinetic and computational study.

Lactonization and proton dissociation of sugar acids take place simultaneously in acidic aqueous solutions. The protonation-deprotonation processes are always fast, whilst the formation and hydrolysis of γ- and δ-lactones are usually slower. Thus, both thermodynamic and kinetic information are required for the complete understanding of these reactions.

The high affinity of small-molecule antioxidants for hemoglobin.

Hemoglobin has previously been shown to display ascorbate peroxidase and urate peroxidase activity, with measurable Michaelis-Menten parameters that reveal a particularly low Km for ascorbate as well as for urate - lower than the respective in vivo concentrations of these antioxidants in blood. Also, direct detection of a hemoglobin-ascorbate interaction was possible by monitoring the 1H-NMR spectrum of ascorbate in the presence of hemoglobin. The relative difference in structures between ascorbate and urate may raise the question as to exactly what the defining structural features would be, for a substrate that binds to hemoglobin with high affinity.

New Class of Hybrid Materials for Detection, Capture, and "On-Demand" Release of Carbon Monoxide.

Carbon monoxide (CO) is both a substance hazardous to health and a side product of a number of industrial processes, such as methanol steam reforming and large-scale oxidation reactions. The separation of CO from nitrogen (N) in industrial processes is considered to be difficult because of the similarities of their electronic structures, sizes, and physicochemical properties (e.g.

The Reaction of Oxy Hemoglobin with Nitrite: Mechanism, Antioxidant-Modulated Effect, and Implications for Blood Substitute Evaluation.

The autocatalytic reaction between nitrite and the oxy form of globins involves free radicals. For myoglobin (Mb), an initial binding of nitrite to the iron-coordinated oxygen molecule was proposed; the resulting ferrous-peroxynitrate species was not detected, but its decay product, the high-valent ferryl form, was demonstrated in stopped-flow experiments. Reported here are the stopped flow spectra recorded upon mixing oxy Hb (native, as well as chemically-derivatized in the form of several candidates of blood substitutes) with a supraphysiological concentration of nitrite.

Deviations from the Most Spherical Deltahedra in Rhenatricarbaboranes Having 2n + 2 Wadean Skeletal Electrons.

Density functional theory studies on the rhenatricarbaboranes CBHRe(CO) (n = 7-12) show that the lowest energy polyhedra for n-vertex metallaboranes having 2n + 2 skeletal electrons and sufficiently dissimilar vertex atoms can deviate from the most spherical closo deltahedra predicted by application of the Wade-Mingos rules. Furthermore, the lowest energy structures of these rhenatricarbaboranes are found to avoid C-C edges and have carbon atoms located at degree 4 rather than degree 5 vertices. The lowest energy structures for the 7-vertex CBHRe(CO) system all have a central CBRe closo deltahedron, namely the pentagonal bipyramid with the rhenium atom at a degree 5 axial vertex and all three carbon atoms at degree 4 equatorial vertices.

Fe(III) - Sulfide interaction in globins: Characterization and quest for a putative Fe(IV)-sulfide species.

The present study reports findings regarding the contrast between HS interaction with bovine hemoglobin (Hb) and horse heart myoglobin (Mb), in terms of binding and dissociation kinetics, affinities, and mechanism. At pH9.5, oxidation of ferric-sulfide adducts in presence of no free sulfide, using hexachloroiridate as oxidant is examined using stopped-flow UV-vis, EPR, vibrational spectroscopy and mass spectrometry.

Pseudo electron-deficient organometallics: limited reactivity towards electron-donating ligands.

Half-sandwich metal complexes are of considerable interest in medicinal, material, and nanomaterial chemistry. The design of libraries of such complexes with particular reactivity and properties is therefore a major quest. Here, we report the unique and peculiar reactivity of eight apparently 16-electron half-sandwich metal (ruthenium, osmium, rhodium, and iridium) complexes based on benzene-1,2-dithiolato and 3,6-dichlorobenzene-1,2-dithiolato chelating ligands.