Cooperativity and halonium transfer in the ternary NCI···CH3I···-CN halogen-bonded complex: An ab initio gas phase study.

CONTEXT: The strength and nature of the two halogen bonds in the NCI···CH3I···-CN halogen-bonded ternary complex are studied in the gas phase via ab initio calculations. Different indicators of halogen bond strength were employed to examine the interactions including geometries, complexation energies, Natural Bond Order (NBO) Wiberg bond indices, and Atoms in Molecules (AIM)-based charge density topological properties. The results show that the halogen bond is strong and partly covalent in nature when CH3I donates the halogen bond, but weak and noncovalent in nature when CH3I accepts the halogen bond. Significant halogen bond cooperativity emerges in the ternary complex relative to the corresponding heterodimer complexes, NCI···CH3I and CH3I···-CN, respectively. For example, the CCSD(T) complexation energy of the ternary complex (-18.27 kcal/mol) is about twice the sum of the complexation energies of the component dimers (-9.54 kcal/mol). The halonium transfer reaction that converts the ternary complex into an equivalent one was also investigated. The electronic barrier for the halonium transfer was calculated to be 6.70 kcal/mol at the CCSD(T) level. Although the MP2 level underestimates and the MP3 overestimates the barrier, their calculated MP2.5 average barrier (6.44 kcal/mol) is close to that of the more robust CCSD(T) level. Insights on the halonium ion transfer reaction was obtained by examining the reaction energy and force profiles along the intrinsic reaction coordinate, IRC. The corresponding evolution of other properties such as bond lengths, Wiberg bond indices, and Mulliken charges provides specific insight on the extent of structural rearrangements and electronic redistribution throughout the entire IRC space. METHODS: The MP2 method was used for geometry optimizations. Energy calculations were performed using the CCSD(T) method. The aug-cc-pVTZ basis set was employed for all atoms other than iodine for which the aug-cc-pVTZ-PP basis set was used instead.

Bariatric Surgery: Current Trends and Newer Surgeries.

Bariatric surgery has evolved and gained in popularity as it has been recognized as the most sustainable and effective treatment for obesity and related diseases. These related diseases are significant causes of obesity related morbidity and mortality. Most bariatric procedures incorporate some component of gastric restriction with or without intestinal bypass, but the full mechanism of these procedures has yet to be elucidated. The most popular surgical procedure remains the sleeve gastrectomy over the last 10 years, while gastric bypass is also still commonly performed. We have also seen growth in revisional bariatric surgery and novel surgical procedures.

Hydrogen-Bond-Driven Peptide Nanotube Formation: A DFT Study.

DFT calculations were carried out to examine geometries and binding energies of H-bond-driven peptide nanotubes. A bolaamphiphile molecule, consisting of two N-α amido glycylglycine head groups linked by either one CH2 group or seven CH2 groups, is used as a building block for nanotube self-assembly. In addition to hydrogen bonds between adjacent carboxy or amide groups, nanotube formation is also driven by weak C-H· · ·O hydrogen bonds between a methylene group and the carboxy OH group, and between a methylene group and an amide O=C group. The intratubular O-H· · ·O=C hydrogen bonds account for approximately a third of the binding energies. Binding energies calculated with the wB97XD/DGDZVP method show that the hydrocarbon chains play a stabilizing role in nanotube self-assembly. The shortest nanotube has the length of a single monomer and a diameter than increases with the number of monomers. Lengthening of the tubular structure occurs through intertubular O-H· · ·O=C hydrogen bonds. The average intertubular O-H· · ·O=C hydrogen bond binding energy is estimated to change with the size of the nanotubes, decreasing slightly towards some plateau value near 15 kcal/mol according to the wB97XD/DGDZVP method.

Bracelet-like Complexes of Lithium Fluoride with Aromatic Tetraamides, and Their Potential for LiF-Mediated Self-Assembly: A DFT Study.

Geometries and binding energies of complexes between a LiF molecule and a model aromatic tetraamide are obtained using various DFT methods. The tetraamide consists of a benzene ring and four amides positioned so that the LiF molecule can bind via Li⋯O=C or N-H⋯F interactions. The complex with both interactions is the most stable one, followed by the complex with only N-H⋯F interactions. Doubling the size of the former resulted in a complex with a LiF dimer sandwiched between the model tetraamides. In turn, doubling the size of the latter resulted in a more stable tetramer with bracelet-like geometry having the two LiF molecules also sandwiched but far apart from each other. Additionally, all methods show that the energy barrier to transition to the more stable tetramer is small. The self-assembly of the bracelet-like complex mediated by the interactions of adjacent LiF molecules is demonstrated by all computational methods employed.

Cholecystocolonic fistula: two different presentations of this rare complication of gallstones.

Cholecystocolonic fistulas (CCF) are a rare but significant complication of biliary disease, frequently presenting as gallstone ileus. Although there is no one agreed-upon procedure, enterolithotomy appears to be the initial treatment of choice; with a subsequent cholecystectomy performed ~4-8 weeks later. Alternatively, a patient may undergo a single-stage procedure, at which time an enterolithotomy, cholecystectomy and fistula closure are performed. Herein, we describe two patients with chronic cholecystitis and subsequent development of CCF with differing presentations. We report the clinical, radiographic and intraoperative findings and discuss the surgical treatment options for each patient, respectively.

Enhancing Effects of the Cyano Group on the C-X∙∙∙N Hydrogen or Halogen Bond in Complexes of X-Cyanomethanes with Trimethyl Amine: CH3-n(CN)nX∙∙∙NMe3, (n = 0-3; X = H, Cl, Br, I).

In this paper, density functional theory and wave function theory calculations are carried out to investigate the strength and nature of the intermolecular C-X∙∙∙N bond interaction as a function of the number of cyano groups, CN, in the X-bond donor while maintaining the X-bond acceptor as fixed. Specifically, complexes of X-cyanomethanes with trimethyl amine CH3-n(CN)nX∙∙∙NMe3 (n = 0-3; X = H, Cl, Br, I) are used as model systems. Geometrical parameters and vibrational C-X-stretching frequencies as well as interaction energies are used as relevant indicators to gauge hydrogen or halogen bond strength in the complexes. Additional characteristics of interactions that link these complexes, i.e., hydrogen or halogen bonds, are calculated with the use of the following theoretical tools: the atoms in molecules (AIM) approach, the natural bond orbital (NBO) method, and energy decomposition analysis (EDA). The results show that, for the specified X-center, the strength of C-X∙∙∙N interaction increases significantly and in a non-additive fashion with the number of CN groups. Moreover, the nature (noncovalent or partly covalent) of the interactions is revealed via the AIM approach.

Sandwich, Triple-Decker and Other Sandwich-like Complexes of Cyclopentadienyl Anions with Lithium or Sodium Cations.

Density functional theory, DFT, calculations were carried out on complexes containing cyclopentadienyl anions and lithium or sodium cations; half-sandwich, sandwich and sandwich-like complexes (among them triple-decker ones) are analyzed. Searches performed through the Cambridge Structural Database revealed that crystal structures containing these motifs exist, mostly structures with sodium cations. The DFT calculations performed here include geometry optimization and frequency calculations of the complexes at the ωB97XD/aug-cc-pVTZ level, followed by the partitioning of the energy of interaction via the Energy Decomposition Analysis scheme, EDA, at the BP86-D3/TZ2P level. Additional calculations and analyses were performed using both the Quantum Theory of Atoms in Molecules, QTAIM, and the Natural Bond Orbital analyses, NBO. The results of this work show that the electrostatic interaction energy is the most important attractive contribution to the total interaction energy of each of the complex systems analyzed here, and that complexation itself leads to minor electron charge shifts.

A Microcosm of Disparities in Breast Cancer: Comparison Between a Private Hospital and a Safety-Net County Hospital Within Los Angeles County.

BACKGROUND: Breast cancer survival is improving due to early detection and treatment advances. However, racial/ethnic differences in tumor biology, stage, and mortality remain. The objective of this study was to analyze presumed disparities at a local level. METHODS: Breast cancer patients at a county hospital and private hospital from 2010 to 2012 were retrospectively reviewed. Demographic, clinical, pathologic, and surgical data were collected. Comparisons were made between hospital cohorts and between racial/ethnic groups from both hospitals combined. RESULTS: 754 patients were included (322 from county hospital and 432 from private hospital). All patients were female. The median age was 54 years at county hospital and 60 years at private hospital (P < .0001). Racial/ethnic minorities comprised 85% of county hospital patients vs. 12% of private hospital patients (P < .0001). County hospital patients had a higher grade, clinical/pathologic stage, HER2-positive rate, and mastectomy rate. Compared to other racial/ethnic groups, non-Hispanic white women were more likely to have lower grade and ER-positive tumors. Hispanic/Latina women were younger and were more likely to have HER2-positive tumors. Both Hispanic/Latina and non-Hispanic black women presented at higher clinical stages and were more likely to undergo neoadjuvant chemotherapy and mastectomy. DISCUSSION: At county hospital compared to private hospital, the proportion of racial/ethnic minorities was higher, and patients presented at younger ages with more aggressive tumors and more advanced disease. The racial/ethnic disparities that were identified locally are largely consistent with those identified in national database studies. These marked differences at hospitals within a diverse city highlight the need for further research into the disparities.

Robotic Inguinal Hernia Repair After Prostatectomy: How to Navigate Safely.

INTRODUCTION: In recent decades, minimally invasive approaches have found their place in treating a specific subset of patients with inguinal hernias, predominantly those with recurrent or bilateral disease. Classically, prior history of urologic pelvic operations, such as prostatectomy, has been listed as relative contraindication for minimally invasive inguinal hernia repair. As the adoption of the robotics platform continues to grow, we aim to outline a feasible robotic-assisted inguinal hernia repair technique in patients with previous prostatectomies. We report the outcomes of 15 patients who underwent repair at 2 institutions. METHODS: This is a retrospective case series of 15 patients who underwent robotic transabdominal preperitoneal approach repair of their inguinal hernias after prostatectomy. Demographics, intraoperative variables, and outcomes of our cases are described. RESULTS: Fifteen patients were included in our cohort. All patients had a history of prostatectomy (7 open, 2 laparoscopic, and 6 robotic) due to prostate cancer. Median age was 70 years old (range: 60 to 89 y), with a median body mass index of 26.3 kg/m2 (range: 20.5 to 37.4 kg/m2). Hernia defects were bilateral in 6 patients and unilateral in the remaining 9 (right; 6, left; 3). The shortest interval between prostatectomy and subsequent hernia repair was 4 months (range: 4 to 216 mo). The median operative time was 139 min (range: 91 to 281 min). All defects were repaired using a polypropylene mesh except in 1 case, where a coated monofilament polyester mesh was used after having a large peritoneal defect to close, preventing future adhesions to the bowel. Mesh sizes used were large (16×11 cm), extra-large (17×12 cm) for anatomic mesh, and 20×15 cm for the monofilament polyester mesh. The mesh was fixed in 14 of 15 cases. Fixation was accomplished with absorbable suture (n=13), barbed suture (n=1), and fibrin sealant (n=1). Peritoneal closure was always performed using a continuous running v-loc suture. There were no documented major intraoperative complications, no 30-day readmission, or recurrences recorded within the follow-up period. Postoperatively, only 2 seromas and 1 hematoma were documented during the follow-up period. CONCLUSIONS: Robotic inguinal hernia repairs in patients with previous prostatectomy is safe and feasible in most patients. Larger patient series are needed to confirm these findings.

Unusual presentation of rectal squamous cell carcinoma perforation-case report and literature review.

This is an unusual case of an obstructive rectal squamous cell carcinoma (SCC), causing perforation and a pelvic abscess, requiring source control and diverting colostomy. A 50-year-old female with chronic constipation presented with worsening right buttock pain for 1 month. On exam, the patient reported right hip tenderness. A computer tomography (CT) revealed rectal wall thickening with a presacral abscess. Due to the concern of rectal perforation with abscess she was taken to the operating room for proctoscopy with biopsy, colostomy diversion and drainage of the abscess over the right buttock. Pathology reported invasive rectal SCC. Rectal SCC presents similarly to rectal adenocarcinoma but its diagnosis must include special markers for cytokeratins. The treatment approach is controversial but adequately treated offers better survival than rectal ADC. Rectal SCC is rare and treated with chemoradiation however it must also be tailored to the variable acute presentations.

Duodenal perforation in the pediatric population: two rare cases at a small community hospital.

Duodenal ulcer perforation is very uncommon in the pediatric population; hence, it is usually not considered in the differential diagnosis of acute abdomen in this age group. In our small community hospital, we had two rare cases of perforated peptic ulcer in the pediatric population within a short span of time. A 14-year-old male and a 13-year-old female child presented to the emergency room with acute abdominal pain. No other symptoms were reported and neither had any history of peptic ulcer disease. Abdominal CT showed pneumoperitoneum consistent with perforated hollow viscus. Subsequent exploratory laparotomy indicated perforated duodenal ulcer in both children. These cases illustrate that perforated peptic ulcers should be considered in children presenting with acute abdomen.

Dedifferentiated liposarcoma of the scrotum. Case report and literature review.

Malignant paratesticular and spermatic cord tumors are rare and often misdiagnosed preoperatively due to clinical presentations similar to other benign scrotal mass etiologies. Only a few cases regarding giant, paratesticular liposarcomas (>10 cm) have been reported. We report a unique case of an aggressive giant dedifferentiated liposarcoma of the scrotum with osteosarcoma features in a 70-year-old patient who initially presented with indolent scrotal swelling. A CT scan showed a large, complex, solid and cystic mass (12.0 x 15.5 x 19.0 cm) in the right scrotum. With a concern of a complex hydrocele, the patient was taken to the operating room for a scrotal approach to excise the hydrocele, but the spermatic cord was not traced to any discernible testicle as the entire mass was indurated and multilocular, and was excised. Pathology revealed a dedifferentiated liposarcoma, with MDM2 amplification. The patient's course was complicated due to metastatic disease.

Cyclic networks of halogen-bonding interactions in molecular self-assemblies: a theoretical N-X...N versus C-X...N investigation.

The geometries and energetics of molecular self-assembly structures that contain a sequential network of cyclic halogen-bonding interactions are investigated theoretically. The strength of the halogen-bonding interactions is assessed by examining binding energies, electron charge transfer (NBO analysis) and electron density at halogen-bond critical points (AIM theory). Specifically, structural motifs having intramolecular N-X...N (X = Cl, Br, or I) interactions and the ability to drive molecular self-assembly via the same type of interactions are used to construct larger self-assemblies of up to three unit motifs. N-X...N halogen-bond cooperativity as a function of the self-assembly size, and the nature of the halogen atom is also examined. The cyclic network of the halogen-bonding interactions provides a suitable cavity rich in electron density (from the halogen atom lone pairs not involved in the halogen bonds) that can potentially bind an electron-deficient species such as a metal ion. This possibility is explored by examining the ability of the N-X...N network to bind Na+. Likewise, molecular self-assembly structures driven by the weaker C-X...N halogen-bonding interactions are investigated and the results compared with those of their N-X...N counterparts.

Concerted halogen bonding and orthogonal metal-halogen interactions in dimers of lithium formamidinate and halogenated formamidines: an ab initio study.

Dimers of lithium formamidinate, CH(NH)2Li, and halogenated formamidines, HN=CHNHX, (X=Cl, Br, or I) are used as model systems to investigate simultaneous N-X···N and N-Li···N interactions, in tandem with orthogonal Li···X interactions. Geometry optimizations and energy calculations for the dimers are examined with the MP2 method and the M06-2X hybrid functional and the aug-cc-pVTZ basis set (the aug-cc-pVTZ-PP basis set is used for the iodine atom). Both methods predict the formation of a planar structure of C2v symmetry, regardless of the identity of the halogen atom. In this structure, the identities of the constituent monomers are essentially lost. Accordingly, the N-X···N interactions emerge as a rather symmetric quasi-linear N···X···N, where the covalent N-X bond in the halogenated formamidine is replaced by a partly covalent N···X interaction. Formation of the C2v structure is also driven by a fairly linear N···Li···N interaction parallel to the N···X···N interaction, and a Li···X interaction orthogonal to both the N···X···N and N···Li···N interactions. The strength of the interactions increases with the size of the halogen. The robustness of the interactions suggests that the dimers studied here or suitable analogues may find diverse applications including their use as novel polymeric synthons.

Folding oligomers of difluorinated thienylfurans: a DFT study.

Density functional theory calculations were performed on a series of difluorinated-thienylfuran oligomers containing up to six repeat units. For any given oligomer, a building unit was chosen to be either in the transoid or in the cisoid conformation. The oligomers are found to be more stable in the all-cisoid conformation as a result of intramolecular F...H hydrogen bonding interactions, as well as stacking pi-pi interactions for the larger oligomers. The relative stability increases markedly with the size of the oligomers, allowing for the adoption of well-defined folding helical patterns for systems with at least five repeat units. Conveniently designed isodesmic reactions show that folding of the oligomers is a thermodynamically favorable process.

Cooperativity in intramolecular bifurcated hydrogen bonds: an ab initio study.

Molecular orbital and density functional theory calculations are performed on some di- and tetrasubstituted derivatives of anthraquinone, dihydrophenazine, and acridone to investigate cooperativity in a pair of bifurcated hydrogen bonds occurring in the same molecule. The various structures were selected as convenient model systems for three-center hydrogen bonding of both H...A...H and A...H...A types. In the former type, the C=O moieties in anthraquinone and acridone act as bifurcated hydrogen bond acceptors, and substituted OH groups act as hydrogen bond donors. In the latter type, the N-H moieties in dihydrophenazine, acridones act as bifurcated hydrogen bond donors, and the carbonyl oxygens of substituted CHO groups act as hydrogen bond acceptors. Different indicators of cooperativity reveal that two intramolecular bifurcated hydrogen bonds simultaneously present in the same molecule significantly reinforce each other.

Conformational stability of a model macrocycle tetraamide: an ab initio study.

Ab initio calculations are carried out to investigate the conformational stability of a model macrocyle tetraamide. The four amide groups in the selected model are present in the sequence: -(O=CNH)-Ph-(NHC=O)-CH=CH-(O=CNH)-Ph-(NHC=O)-CH=CH-. In this sequence, two phenyl rings and two ethene groups act as bridges between the amide units. Each amide motif bonds to a phenyl ring through its amide nitrogen and to an ethene group through its amide carbon. Four clearly distinct minimum-energy conformations are found upon full geometry optimization using the B3LYP/6-31+G(d) method. Frequency calculations using the same method confirm that the four conformations are indeed minima in the macrocycle potential energy surface. Relative to the most stable conformer, the other conformations are higher in energy by 0.86, 2.09, and 9.17 kcal/mol, respectively, at the MP2/6-31+G(d,p) level. The stability of the macrocycle conformations is correlated primarily to the existence and strength of intramolecular N-H...O=C hydrogen bonds. Additional stability to the conformations is found to come from weak Ph-H...O=C hydrogen bonding between a carbonyl oxygen and a hydrogen atom of a phenyl group. Solvent effects play an important role in the relative energies of the various conformations, as indicated by the simple SCRF = dipole model calculations for the case of aqueous solution.

Cooperative effects in two-dimensional ring-like networks of three-center hydrogen bonding interactions.

Cooperative effects in two-dimensional cyclic networks containing intermolecular three-centered hydrogen bonding interactions of the type H1...A...H2 are investigated by means of ab intio molecular orbital and density functional theory calculations. Ring-like clusters consisting of three and up to nine monomers of the cis-cis isomer of carbonic acid H2CO3 are used as basic models, where each unit acts simultaneously as a double hydrogen-bond donor and double hydrogen-bond acceptor. Cooperative effects based on binding energies are evident for (H2CO3)n, where n goes from 2 to 9. Thus, the ZPVE-corrected dissociation energy per bifurcated hydrogen bond increases from 11.52 kcal/mol in the dimer to 20.42 kcal/mol in the nonamer, i.e., a 77% cooperative enhancement. Cooperative effects are also manifested in such indicators as geometries, and vibrational frequencies and intensities. The natural bond orbital analysis method is used to rationalize the results in terms of the substantial charge delocalization taking place in the cyclic clusters. Cooperativity seems close to reaching an asymptotic limit in the largest ring considered, n = 9.

A comparative ab initio study of intramolecular proton transfer in model alpha-hydroxyalkoxides.

A comparative ab initio study was performed on the intramolecular proton-transfer reaction that occurs in alpha-hydroxyethanoxy, alpha-hydroxyphenoxide, and alpha-hydroxyethenoxy anions. The intramolecular proton transfer occurs in a five-member atom arrangement, between two oxygen atoms separated by a carbon-carbon bond. The chosen systems serve as models for alpha-hydroxyalkoxide molecules where the carbon-carbon bond varies from a single bond (the glycolate anion or alpha-hydroxyethanoxide anion) to a part of an aromatic ring (the alpha-hydroxyphenoxide anion), and finally to a double bond (the alpha-hydroxyethenoxide anion). Particular attention was given to the evolution along the intrinsic reaction coordinate of such properties as energies, relevant structural parameters, Mulliken charges, dipole moments, and 1H-NMR chemical shifts to reveal the similarities and differences for the proton transfer in the model systems.

Creating nanocavities of tunable sizes: hollow helices.

A general strategy for creating nanocavities with tunable sizes based on the folding of unnatural oligomers is presented. The backbones of these oligomers are rigidified by localized, three-center intramolecular hydrogen bonds, which lead to well-defined hollow helical conformations. Changing the curvature of the oligomer backbone leads to the adjustment of the interior cavity size. Helices with interior cavities of 10 A to >30 A across, the largest thus far formed by the folding of unnatural foldamers, are generated. Cavities of these sizes are usually seen at the tertiary and quaternary structural levels of proteins. The ability to tune molecular dimensions without altering the underlying topology is seen in few natural and unnatural foldamer systems.