Understanding the role of crosslink density and linear viscoelasticity on the shear failure of pressure-sensitive-adhesives.

Pressure-sensitive-adhesives (PSAs) are ubiquitous in electronic, automobile, packaging, and biomedical applications due to their ability to stick to numerous surfaces without undergoing chemical reactions. Although these materials date back to the 1850s with the development of surgical tapes based on natural rubber, their resistance to shear loads remains challenging to predict from molecular design. This work investigates the role of crosslink density on the shear resistance of model PSAs based on poly(2-ethylhexyl acrylate-co-acrylic acid) physically crosslinked with aluminum acetylacetonate. The key result is that crosslinking PSAs leads to notable stress concentrations ahead of the peel front, as well as a transition from cohesive to adhesive failure. The shear stress distributions, as evaluated by means of a linearly viscoelastic shear lag model, suggest that this transition is related to the evolution of the ratio of the load transfer length to the bond length as dictated by the mechanical properties of the backing and adhesive layers, and the geometry of the tape.

Is postoperative radiotherapy (PORT) a viable option in high-risk early-stage cervical cancer after upfront or downstaged radical surgery? A comparative study.

BACKGROUND: Radical surgery for cervical cancer has inherent benefits, and as upfront or post neoadjuvant chemotherapy (NACT), is extendable to locally advanced cancer cervix (LACC), with postoperative radiotherapy (PORT) for high-risk factors. Objective of the study was to compare the effectiveness and survival between non-PORT and PORT in high-risk early stages. MATERIALS AND METHODS: Radical hysterectomies conducted between January 2014 and December 2017 were evaluated and followed till December 2019. Clinical, surgical-pathologic characteristics, and oncological outcomes were compared between non-PORT and PORT groups. A similar comparison was made between alive and dead patients within each group. The impact of PORT was assessed. RESULTS: Of 178 radical surgeries, early-LACC constituted 70%. Most (37%) of the patients belonged to stage 1b2, while stage 2b formed 5%. Mean age of patients was 46.5 years; 69% were below 50 years of age. Abnormal bleeding (41%) was the predominant symptom, followed by postcoital (20%) and postmenopausal bleeding (12%). Upfront surgeries formed 70.2%, and the average waiting period was 1.93 months (range: 1-10 months). PORT patients were 97 (54.5%) in number and the remaining formed the non-PORT group. Mean follow-up was 34 months, with 118 (66%) alive patients. Significant adverse prognostic factors were tumors >4 cm (44.4% patients), positive margins (10%), lymphatic vascular space invasion (LVSI; 42%), malignant nodes (33%), multiple metastatic nodes averaging seven (range: 3-11), and delayed (>6 months) presentation, but not deep stromal invasion (77% patients) and positive parametrium (8.4% patients). PORT overcame the adverse effects of tumors >4 cm, multiple metastatic nodes, positive margins, and LVSI. Total recurrences (25%) were balanced for both groups, but recurrences within 2 years were significantly more for PORT. Two-year overall survival (78%) and recurrence-free survival (72%), median overall survival (21 months), and median recurrence-free interval (19 months) were significantly better for PORT, with the complication rates being similar. CONCLUSION: PORT had significantly better oncological outcomes compared to non-PORT. Multimodal management is worthwhile.

Review on host-pathogen interaction in dermatophyte infections.

Dermatophytosis is a common superficial fungal infection of the skin and its appendages caused by dermatophytes. Recent times have witnessed a dynamic evolution of dermatophytes driven by their ecology, reproduction, pathogenicity and host immune response, influenced by population migration and socioeconomic status. Dermatophytes establish infection following successful adherence of arthroconidia to the surface of keratinized tissues. The proteolytic enzymes released during adherence and invasion not only ascertain their survival but also allow the persistence of infection in the host. While the cutaneous immune surveillance mechanism, after antigen exposure and presentation, leads to activation of T lymphocytes and subsequent clonal expansion generating effector T cells that differentially polarize to a predominant Th17 response, the response fails to eliminate the pathogen despite the presence of high levels of IFN-γ. In chronic dermatophytosis, antigens are a constant source of stimulus promoting a dysregulated Th17 response causing inflammation. The host-derived iTreg response fails to counterbalance the inflammation and instead polarizes to Th17 lineage, aggravating the chronicity of the infection. Increasing antifungal resistance and recalcitrant dermatophytosis has impeded the overall clinical remission. Human genetic research has the potential to generate knowledge to explore new therapeutic targets. The review focuses on understanding specific virulence factors involved in pathogenesis and defining the role of dysregulated host immune response against chronic dermatophytic infections for future management strategies.

A Snapshot of T Cell Subset Cytokines in Pemphigus Vulgaris: A Cross-Sectional Study.

OBJECTIVE: The purpose of this study was to assess the serum levels of cytokines produced by the Th1 (IFN-γ, IL-12), Th2 (IL-4), Th17 (IL-6, IL-17A, IL-23), and Treg (IL-10 and TGF-ß) pathways in individuals with active pemphigus vulgaris (PV) and to determine whether these levels were correlated with the severity of the disease condition. PATIENTS AND METHODS: This study was conducted with 90 individuals, of which 50 were PV patients and 40 healthy individuals (age and gender-matched) as controls. Serum samples were collected and tested for cytokine levels by ELISA (enzyme-linked immunosorbent assay). The cytokine levels in the serum of PV patients and healthy controls were compared statistically using the Mann-Whitney test for nonparametric samples. The strength of the association between the variables was evaluated using the Spearman correlation test. RESULTS: The mean serum levels of IFN- γ (p < 0.001), IL-6 (p < 0.001), IL-10 (p < 0.001), IL-12 (p < 0.05), and IL-17 (p < 0.001) were significantly higher and TGF-ß were significantly low in the PV patients than those observed in the control group. The mean concentration of serum IL-4 in patients with PV did not differ from those in the control group. CONCLUSIONS: In active PV, the Th1 and Th17 pathways are involved in the development and progression of the disease, whereas the Th2 pathway is blocked. Both of these pathways play a significant role in the disease. It is possible that the Treg pathway acts as an antagonist to the Th1 and Th17 pathways, which would cause the disease to become more localised. This study lays the foundation for a better understanding of the aetiology of PV and implies that cytokines could be used as potential therapeutic targets and disease activity biomarkers.

Molecular approaches to lung cancer prevention.

Lung cancer is generally diagnosed at advanced stages when surgical resection is not possible. Late diagnosis, along with development of chemoresistance, results in high mortality. Preventive approaches, including smoking cessation, chemoprevention and early detection are needed to improve survival. Smoking cessation combined with low-dose computed tomography screening has modestly improved survival. Chemoprevention has also shown some promise. Despite these successes, most lung cancer cases remain undetected until advanced stages. Additional early detection strategies may further improve survival and treatment outcome. Molecular alterations taking place during lung carcinogenesis have the potential to be used in early detection via noninvasive methods and may also serve as biomarkers for success of chemopreventive approaches. This review focuses on the utilization of molecular biomarkers to increase the efficacy of various preventive approaches.

Biofilm-Formation in Clonally Unrelated Multidrug-Resistant Acinetobacter baumannii Isolates.

This study analyzed the genotype, antibiotic resistance, and biofilm formation of Acinetobacter baumannii strains and assessed the correlation between biofilm formation, antibiotic resistance, and biofilm-related risk factors. A total of 207 non-replicate multi-drug-resistant A. baumannii strains were prospectively isolated. Phenotypic identification and antimicrobial susceptibility testing were carried out. Isolate biofilm formation ability was evaluated using the tissue culture plate (TCP), Congo red agar, and tube methods. Clonal relatedness between the strains was assessed by enterobacterial repetitive intergenic consensus-PCR genotyping. Of the 207 isolates, 52.5% originated from an intensive care unit setting, and pan resistance was observed against ceftazidime and cefepime, with elevated resistance (99-94%) to piperacillin/tazobactam, imipenem, levofloxacin, and ciprofloxacin. alongside high susceptibility to tigecycline (97.8%). The Tissue culture plate, Tube method, and Congo red agar methods revealed that 53.6%, 20.8%, and 2.7% of the strains were strong biofilm producers, respectively, while a significant correlation was observed between biofilm formation and device-originating respiratory isolates (p = 0.0009) and between biofilm formation in colonized vs. true infection isolates (p = 0.0001). No correlation was detected between antibiotic resistance and biofilm formation capacity, and the majority of isolates were clonally unrelated. These findings highlight the urgent need for implementing strict infection control measures in clinical settings.

Recent Nano-based Therapeutic Intervention of Bioactive Sesquiterpenes: Prospects in Cancer Therapeutics.

In the recent scenario, nanotechnology-based therapeutics intervention has gained tremendous impetus all across the globe. Nano-based pharmacological intervention of various bioactive compounds has been explored on an increasing scale. Sesquiterpenes are major constituents of essential oils (EOs) present in various plant species which possess intriguing therapeutic potentials. However, owing to their poor physicochemical properties; they have pharmacological limitations. Recent advances in nano-based therapeutic interventions offer various avenues to improve their therapeutic applicability. Reckoning with these, the present review collates various nano-based therapeutic intervention of sesquiterpenes with prospective potential against various debilitating diseases especially cancer. In our viewpoint, considering the burgeoning advancement in the field of nanomedicine; in the near future, the clinical applicability of these nano-formulated sesquiterpenes can be foreseen with great enthusiasm.

Current Nanoparticle Approaches in Nose to Brain Drug Delivery and Anticancer Therapy - A Review.

Nanoparticles (NPs) are unique may be organic or inorganic, play a vital role in the development of drug delivery targeting the central nervous system (CNS). Intranasal drug delivery has shown to be an efficient strategy with attractive application for drug delivery to the CNS related diseases, such as Parkinson's disease, Alzheimer 's disease and brain solid tumors. Blood brain barrier (BBB) and blood-cerebrospinal fluid barriers are natural protective hindrances for entry of drug molecules into the CNS. Nanoparticles exhibit excellent intruding capacity for therapeutic agents and overcome protective barriers. By using nanotechnology based NPs targeted, drug delivery can be improved across BBB with discharge drugs in a controlled manner. NPs confer safe from degradation phenomenon. Several kinds of NPs are used for nose to the brain (N2B) enroute, such as lipidemic nanoparticles, polymeric nanoparticles, inorganic NPs, solid lipid NPs, dendrimers. Among them, popular lipidemic and polymeric NPs are discussed, and their participation in anti-cancer activity has also been highlighted in this review.

Low Temperature-Mediated Enhancement of Photoacoustic Imaging Depth.

We study the temperature dependence of the underlying mechanisms related to the signal strength and imaging depth in photoacoustic imaging. The presented theoretical and experimental results indicate that imaging depth can be improved by lowering the temperature of the intermediate medium that the laser passes through to reach the imaging target. We discuss the temperature dependency of optical and acoustic properties of the intermediate medium and their changes due to cooling. We demonstrate that the SNR improvement of the photoacoustic signal is mainly due to the reduction of Grüneisen parameter of the intermediate medium which leads to a lower level of background noise. These findings may open new possibilities toward the application of biomedical laser refrigeration.

Assessment and optimization of liver volume before major hepatic resection: Current guidelines and a narrative review.

Post hepatectomy liver failure (PHLF) remains a significant cause of morbidity and mortality after major liver resection. Although the etiology of PHLF is multifactorial, an inadequate functional liver remnant (FLR) is felt to be the most important modifiable predictor of PHLF. Pre-operative evaluation of FLR function and volume is of paramount importance before proceeding with any major liver resection. Patients with inadequate or borderline FLR volume must be considered for volume optimization strategies such as portal vein embolization (PVE), two stage hepatectomy with portal vein ligation (PVL), Yttrium-90 radioembolization, and associating liver partition and portal vein ligation for staged hepatectomy (ALPPS). This paper provides an overview of assessing FLR volume and function, and discusses indications and outcomes of commonly used volume optimization strategies.

FcɛR1α gene polymorphism shows association with high IgE and anti-FcɛR1α in Chronic Rhinosinusitis with Nasal Polyposis.

Despite large number of investigations, the etiology of chronic rhinosinusitis (CRS) remains unclear. Several factors are likely involved in its onset. The genetic susceptibility of IgE-responsiveness likely caused by polymorphism(s) in high affinity receptor for IgE (FcɛR1α) gene can help in understanding the pathophysiology of CRS with nasal polyposis (CRSwNP). A population-based case-control association analysis was conducted to assess the risk of CRSwNP conferred by single nucleotide polymorphisms (SNPs) in FcɛR1α gene in a North Indian cohort. Two promoter and three exonic regions of FcɛR1α gene were amplified and sequenced to investigate five SNPs: rs2427827, rs2251746, rs2298804, rs2298805, and rs2269718. BLAST analysis and subsequent multiple alignments, with known sequences available in the NCBI database, were performed. Total serum IgE and FcɛR1α antibody levels were estimated. Patient IgE level of 461.22 ± 436.43 in comparison to 83.62 ± 58.043 IU/mL in controls (P < 0.0001), and FcɛR1α antibody level of 292.38 ± 115.27 in comparison to 160.56 ± 105.9 in controls (P < 0.0001), depicts their highly significant associations with CRSwNP disease. However, no SNP showed evidence of association with CRSwNP; although relatively higher Odds ratios were observed with rs2427827, rs2251746, and rs2298804. Patient stratification revealed a significant association (P < 0.05) of rs2427827 SNP with high IgE level CRSwNP patients. Nonetheless, we found no SNP associated with low serum IgE level patients. SNP (rs2427827) in the FcɛR1α gene region and high IgE levels may confer susceptibility to CRSwNP in north Indian population. However, further studies including larger sample size, gene-gene, and gene-environment interactions are required for its elucidation.

Green synthesis of Al2O3 nanoparticles and their bactericidal potential against clinical isolates of multi-drug resistant Pseudomonas aeruginosa.

The high prevalence of extended-spectrum ß-lactamases (76.3 %) and metallo-ß-lactamases (7.3 %) amongst the bacteria Pseudomonas aeruginosa is a critical problem that has set forth an enormous therapeutic challenge. The suggested role of nanoparticles as next generation antibiotics, and inadequate information on antibacterial activity of aluminium oxide nanoparticles has led us to investigate the green synthesis of aluminium oxide nanoparticles (Al2O3 NPs) using leaf extracts of lemongrass and its antibacterial activity against extended-spectrum ß-lactamases and metallo-ß-lactamases clinical isolates of P. aeruginosa. The synthesized Al2O3-NPs were characterized by scanning electron microcopy, high resolution-transmission electron microscopy, atomic force microscopy, X-ray diffraction, Zeta potential, and differential light scattering techniques. The X-ray diffraction data revealed the average size of the spherical Al2O3-NPs as 34.5 nm. The hydrodynamic size in Milli Q water and Zeta potential were determined to be 254 nm and +52.2 mV, respectively. The minimal inhibitory concentration of Al2O3-NPs was found to be in the range of 1,600-3,200 µg/ml. Treatment at concentrations >2,000 µg/ml, resulted in complete growth inhibition of extended-spectrum ß-lactamases and metallo-ß-lactamases isolates. Scanning electron microcopy analysis revealed the clusters of nanoparticles attached to the bacterial cell surface, causing structural deformities in treated cells. High resolution-transmission electron microscopy analysis confirmed that nanoparticles crossed the cell membrane to become intracellular. The interaction of nanoparticles with the cell membrane eventually triggered the loss of membrane integrity, most likely due to intracellular oxidative stress. The data explicitly suggested that the synthesized Al2O3-NPs can be exploited as an effective bactericidal agent against extended-spectrum ß-lactamases, non-extended-spectrum ß-lactamases and metallo-ß-lactamases strains of P. aeruginosa, regardless of their drug resistance patterns and mechanisms. The results elucidated the clinical significance of Al2O3-NPs in developing an effective antibacterial therapeutic regimen against the multi-drug resistant bacterial infections. The use of leaf extract of lemongrass for the synthesis of Al2O3-NPs appears to be cost effective, nontoxic, eco-friendly and its strong antibacterial activity against multi-drug resistant strains of P. aeruginosa offers compatibility for pharmaceutical and other biomedical applications.

Molecular interaction of human brain acetylcholinesterase with a natural inhibitor huperzine-B: an enzoinformatics approach.

The present study emphasizes the molecular interactions between human brain acetylcholinesterase (AChE) and the natural ligand Huperzine-B and its comparison to 'AChE-Tolserine interactions'. Docking between Huperzine-B and AChE was performed using 'Autodock4.2'. Hydrophobic interactions and hydrogen bonds both play an equally important role in the correct positioning of Huperzine-B within the 'catalytic site' of AChE to permit docking. However, docking of Tolserine to AChE is largely dominated by hydrophobic interactions. Such information may aid in the design of versatile AChE-inhibitors, and is expected to aid in safe clinical use of Huperzine-B. Scope still remains in the determination of the three-dimensional structure of AChE-Huperzine-B complex by X-ray crystallography to validate the described data. Furthermore, this study confirms that Huperzine-B is a more efficient inhibitor of human brain AChE compared to tolserine with reference to Ki and ΔG values.

Prediction of comparative inhibition efficiency for a novel natural ligand, galangin against human brain acetylcholinesterase, butyrylcholinesterase and 5-lipoxygenase: a neuroinformatics study.

The present study elucidates molecular interactions of human acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) and 5-lipoxygenase (5-LPO) with a novel natural ligand Galangin (GAL); and also with the well-known ligands Bisnorcymserine (BNC) and Cymserine for comparison. Docking between these ligands and enzymes were performed using 'Autodock4.2'. It was found that hydrophobic interactions play an important role in the correct positioning of BNC within the 'catalytic site' of AChE, BuChE and 5-LPO to permit docking while hydrogen bonds are significant in case of cymserine for the same. However, only polar interactions are significant in the correct positioning of GAL within the 'catalytic site' of AChE, BuChE and 5-LPO to permit docking. Such information may aid in the design of versatile AChE, BuChE and 5 LPO-inhibitors, and is expected to aid in safe clinical use of above ligands. Scope still remains in the determination of the three-dimensional structure of AChE-GAL, BuChE-GAL and 5-LPO-GAL complex by X-ray crystallography to certify the described data. Moreover, the present study confirms that GAL is a more efficient inhibitor of human brain AChE compared to BNC and cymserine, while in case of 5-LPO and human brain BuChE, BNC is a more efficient inhibitor compared to GAL and cymserine with reference to ΔG and Ki values.

Expression of the full-length HCV core subgenome from HCV gentoype-1a and genotype-3a and evaluation of the antigenicity of translational products.

BACKGROUND: Hepatitis C virus (HCV) infection is a major public health problem in India. Detection of HCV and its genotypes by simple and economic assays is a prime requirement in the planning of antiviral treatments for patients infected with this virus. Although commercial assays are available for the detection of both HCV RNA and genotypes, efforts aimed at the development of simple and economical systems for these measurements are still going on. AIM: The present study was designed to clone and express the HCV CORE gene from HCV genotype-1a and genotype-3a and use the peptides to develop immunoassays for the detection of genotype-specific antibodies in sera samples. METHODS: One hundred and thirty-five serum samples from patients with liver and renal diseases were screened for HCV RNA by real-time PCR, followed by HCV genotyping in RNA-positive sera by restriction fragment length polymorphism, sequencing, and phylogenetic analysis. The HCV CORE gene was amplified from sera carrying HCV genotype-1a and genotype-3a and cloned and expressed in the pET19b vector. The translational products were used to develop a western blot assay for the detection of genotype-specific anti-HCV antibodies. RESULTS: The HCV CORE gene, from both genotypes, was cloned and expressed successfully, with production of a 26 kDa recombinant protein in either case. Using peptides in a western blot assay, 101 sera samples were tested for the anti-HCV CORE antibody. Each peptide showed a reaction with anti-HCV total antibody without showing any genotype-specific binding. This indicates that individual peptides obtained from different genotypes do not have a genotype-specific epitope to bind with antibodies. CONCLUSION: Cloning and expression of the HCV CORE gene from genotype-1a and genotype-3a was successful. However, the peptides formed did not show genotype-specific binding with anti-HCV.

Synthesis of Zirconium Aryloxide Complexes Containing Pendent Vinyl Groups.

The attachment of pendent olefin groups to oxygen-ligated zirconium complexes using olefin-substituted phenols and alcohols and readily accessible zirconium reagents is described. Syntheses of three crystallographically characterizable complexes isolable in 55-90% yield are reported. Eugenol, HOC(6)H(3)(OMe-2)(CH(2)CH=CH(2)-4) (HOAr) reacts with [Zr(O(i)Pr)(4)(HO(i)Pr)](2) in toluene to form [((i)PrO)(2)(ArO)Zr(&mgr;-O(i)Pr)](2), 1. CH(2)=CHCH(2)OH reacts with [Zr(NMe(2))(4)](2) in the presence of 2,6-dimethylphenol to form the mixed ligand salt, {Me(2)NH(2)}{[(2,6-Me(2)C(6)H(3)O)(3)Zr](2)(&mgr;-OCH(2)CH=CH(2))(3)}, 2. The potassium salt derived from eugenol, KOAr, reacts with "Zr(OEt)(4)" in THF to form [K(2)Zr(OAr)(4)(OEt)](2)(O), 3.

Utility of Arylamido Ligands in Yttrium and Lanthanide Chemistry(1).

The reactivity of KNHAr reagents (Ar = C(6)H(5), C(6)H(3)Me(2)-2,6, C(6)H(3)(i)Pr(2)-2,6) with lanthanide and yttrium trichlorides has been investigated. With the larger metals Nd and Sm and the smaller 2,6-dimethyl-substituted ligand, the bimetallic dianionic complexes [K(THF)(6)](2)[Ln(&mgr;-NHC(6)H(3)Me(2)-2,6)(NHC(6)H(3)Me(2)-2,6)(3)](2) (Ln: Sm, 1a; Nd, 1b) are isolated as the potassium salts. Under the same reaction conditions YCl(3) forms a bimetallic anion which retains chloride: [K(DME)(2)(THF)(3)][Y(2)(&mgr;-NHC(6)H(3)Me(2)-2,6)(2)(&mgr;-Cl)(NHC(6)H(3)Me(2)-2,6)(4)(THF)(2)], 2. With the larger 2,6-diisopropyl ligands, neutral complexes are isolated in both solvated monometallic and unsolvated bimetallic forms. With Nd, a distorted octahedral trisolvate, Nd(NHC(6)H(3)(i)Pr(2)-2,6)(3)(THF)(3), 3, was obtained, whereas with Yb and Y the trigonal bipyramidal disolvates, Ln(NHC(6)H(3)(i)Pr(2)-2,6)(3)(THF)(2) (Ln: Yb, 4a; Y, 4b), were isolated. THF-free complexes of the NHC(6)H(3)(i)Pr(2)-2,6 ligand are available by reacting the amine NH(2)C(6)H(3)(i)Pr(2)-2,6 with Ln[N(SiMe(3))(2)](3) complexes. By this route, the dimers [Ln(&mgr;-NHC(6)H(3)(i)Pr(2)-2,6)(NHC(6)H(3)(i)Pr(2)-2,6)(2)](2) (Ln: Yb, 5a; Y, 5b) were isolated. The reaction of the unsubstituted arylamido salt KNHC(6)H(5) with NdCl(3) produced an insoluble material which was characterized as [Nd(NHC(6)H(5))(3)(KCl)(3)], 6. 6 reacted with Al(2)Me(6) in hexanes and produced a heteroleptic mixed-metal complex {[Me(2)Al(&mgr;-Me(2))](2)Nd(&mgr;(3)-NC(6)H(5))(&mgr;-Me)AlMe}(2), 7, and the trimeric aluminum arylamido complex [Me(2)Al(&mgr;-NHC(6)H(5))](3), 8. The solvent of crystallization and relevant crystallographic data for the compounds identified by X-ray analysis follow: 1a,THF, 156 K, P2(1)/n, a = 12.985(2) Å, b = 27.122(5) Å, c = 17.935(3) Å, beta = 100.19(1) degrees, V = 6216(1) Å(3), Z = 2, 6148 reflections (I > 3sigma(I)), R(F)() = 7.1%; 1b,THF, 156 K, P2(1)/n, a = 12.998(2) Å, b = 27.058(3) Å, c = 17.962(2) Å, beta = 99.74(1) degrees, V = 6225(1) Å(3), Z = 2; 2,DME/hexanes, P2(1)/n, a = 23.335(2) Å, b = 12.649(1) Å, c = 27.175(3) Å, beta = 96.36(1) degrees, V = 7971(1) Å(3), Z = 4, 2788 reflections (I > 3sigma(I)), R(F)() = 9.5%; 3, THF, P2(1), a = 12.898(1) Å, b = 16.945(1) Å, c = 13.290(1) Å, beta = 118.64(2) degrees, V = 2549.3(3) Å(3), Z = 2, 3414 reflections (I > 3sigma(I)), R(F)() = 4.3%; 4a, hexanes, P2(1), a = 9.718(2) Å, b = 19.119(3) Å, c = 12.640(2) Å, beta = 112.08(1) degrees, V = 2176.3(6) Å(3), Z = 2, 2933 reflections (I > 3sigma(I)), R(F)() = 4.3%; 4b, hexanes, 158 K, a = 9.729(2) Å, b = 19.095(5) Å, c = 12.744(1) Å, beta = 112.11(1) degrees, V = 2193.4(6) Å(3); 5b, hot toluene, 158 K, P2(1), a =19.218(9) Å, b = 9.375(3) Å, c = 19.820(5) Å, beta = 110.25(2) degrees, V = 3350(2)Å(3), Z = 2, 1718 reflections (I > 2sigma (I)), R1 = 9.7%; 7, hexanes, 156 K, P&onemacr;, a = 9.618(3) Å, b = 12.738(4) Å, c = 9.608(3) Å, alpha = 99.32(1) degrees, beta = 108.87(1) degrees, gamma = 94.23(1) degrees, V = 1089.1(6) Å(3), Z = 2, 2976 reflections (I > 3sigma(I)), R(F)() = 3.9%; 8, hexanes, 156 K, Pcab, a = 23.510(5) Å, b = 25.462(5) Å, c = 8.668(2) Å, V = 5188(1) Å(3), Z = 8, 1386 reflections (I > 3sigma(I)), R(F)() = 5.7%.

Synthesis, Reactivity, and Structural Characterization of the Nonclassical [MTe(7)](n)()(-) Anions (M = Ag, Au, n = 3; M = Hg, n = 2).

Several tellurometalates of the general formula [MTe(7)](n)()(-) (n = 2, 3) have been isolated as salts of organic cations by reaction of suitable metal sources with polytelluride solutions in DMF. The [HgTe(7)](2)(-) anion has the same structure in both the NEt(4)(+) and the PPh(4)(+) salts except for a minor change in the ligand conformation. The [AgTe(7)](3)(-) and [HgTe(7)](2)(-) anions contain metal atoms coordinated in trigonal-planar fashion to eta(3)-Te(7)(4)(-) ligands. The central Te atom of an eta(3)-Te(7)(4)(-) ligand is coordinated to the metal atom and to two Te atoms in a "T"-shaped geometry consistent with a hypervalent 10 e(-) center. The planar [AuTe(7)](3)(-) anion may best be described as possessing a square-planar Au(III) atom coordinated to an eta(3)-Te(5)(4)(-) ligand and to an eta(1)-Te(2)(2)(-) ligand. The reaction of [NEt(4)](n)()[MTe(7)] (M = Hg, n = 2; M = Au, n = 3) with the activated acetylene dimethyl acetylenedicarboxylate (DMAD) has yielded the products [NEt(4)](n)()[M(Te(2)C(2)(COOCH(3))(2))(2)] (M = Hg, n = 2; M = Au, n = 1). The metal atoms are coordinated to two Te(COOCH(3))C=C(COOCH(3))Te(2)(-) ligands, for M = Hg in a distorted tetrahedral fashion and for M = Au in a square-planar fashion.