The influence of device handles in single-molecule experiments.

We deduce a fully analytical model to predict the artifacts of the device handles in single molecule force spectroscopy experiments. As we show, neglecting the handle stiffness can lead to crucial overestimation or underestimation of the stability properties and unfolding thresholds of multistable molecules.

Broadband stimulated Raman microscopy with 0.1 ms pixel acquisition time.

Femtosecond stimulated Raman microscopy (FSRM) is a nonlinear technique for rapid broadband Raman imaging. It utilizes a few femtosecond probe pulse and a narrow bandwidth pump pulse. Using a fast (20 kHz) multi-channel detector, stimulated Raman spectra can be recorded with an acquisition time as short as 0.1 ms. In this Letter, spectra of neat benzonitrile at different acquisition speeds are presented to benchmark the FSRM setup. Furthermore, chemical maps of a multi-phase polymer blend are recorded using the fastest acquisition rate possible with the current instrument.

Polarized 3D Raman and nanoscale near-field optical microscopy of optically inscribed surface relief gratings: chromophore orientation in azo-doped polymer films.

We have used polarized confocal Raman microspectroscopy and scanning near-field optical microscopy with a resolution of 60 nm to characterize photoinscribed grating structures of azobenzene doped polymer films on a glass support. Polarized Raman microscopy allowed determining the reorientation of the chromophores as a function of the grating phase and penetration depth of the inscribing laser in three dimensions. We found periodic patterns, which are not restricted to the surface alone, but appear also well below the surface in the bulk of the material. Near-field optical microscopy with nanoscale resolution revealed lateral two-dimensional optical contrast, which is not observable by atomic force and Raman microscopy.

Multipurpose Iron-Chelating Ligands Inspired by Bioavailable Molecules.

Because of their capacity to bind metals, metal chelators are primarily employed for therapeutic purposes, but they can also find applications as colorimetric reagents and cleaning solutions as well as in soil remediation, electroplating, waste treatment, and so on. For instance, iron-chelation therapy, which is used to treat iron-overload disorders, involves removing excess iron from the blood through the use of particular molecules, like deferoxamine, that have the ability to chelate the metal. The creation of bioinspired and biodegradable chelating agents is a crucial objective that draws inspiration from natural products. In this context, starting from bioavailable molecules such as maltol and pyrogallol, new molecules have been synthetized and characterized by potentiometry, infrared spectroscopy and cyclic voltammetry. Finally, the ability of these to bind iron has been investigated, and the stability constants of ferric complexes are measured using spectrophotometry. These compounds offer intriguing scaffolds for an innovative class of versatile, multipurpose chelating agents.

A predictive model for the thermomechanical melting transition of double stranded DNA.

By extending the classical Peyrard-Bishop model, we are able to obtain a fully analytical description for the mechanical response of DNA under stretching at variable values of temperature, number of base pairs and intrachains and interchains bonds stiffness. In order to compare elasticity and temperature effects, we first analyze the system in the zero temperature mechanical limit, important to describe several experimental effects including possible hysteresis. We then analyze temperature effects in the framework of equilibrium Statistical Mechanics. In particular, we obtain an analytical expression for the temperature-dependent melting force and unzipping assigned displacement in the thermodynamical limit, also depending on the relative stability of intra vs. inter molecular bonds. Such results coincide with the purely mechanical model in the limit of zero temperature and with the denaturation temperature that we obtain with the classical transfer integral method. Based on our analytical results, we obtain explicitly phase diagrams and cooperativity parameters, where also discreteness effect can be accounted for. The obtained results are successfully applied in reproducing the thermomechanical experimental melting of DNA and the response of DNA hairpins. Due to the generality of the model, exemplified in the proposed analysis of both overstretching and unzipping experiments, we argue that the proposed approach can be extended to other thermomechanically induced molecular melting phenomena. STATEMENT OF SIGNIFICANCE: We obtain a fully analytical description of the complex wiggly energy landscape of two stranded macromolecules under unzipping loading. Based on Equilibrium Statistical Mechanics, we describe the combined thermomechanical effects and the melting transition of double stranded molecules such as nucleic acids. This is proved by quantitatively predicting the experimental behavior of both melting of DNA and DNA hairpins opening. While analytical results have been previously attained under special conditions on the relative stiffness of the covalent vs. non-covalent bonds of the base pairs, our model is completely general in this respect, thus representing a tool in the perspective of the design at the molecular scale. We show that the obtained model can be fully inscribed in the theory of phase transitions giving a new interpretation of the thermomechanical behavior of double stranded molecules.

Cooperative melting in double-stranded peptide chains through local mechanical interactions.

The separation of double-stranded peptide chains can occur in two ways: cooperatively or non-cooperatively. These two regimes can be driven either by chemical or thermal effects, or through non-local mechanical interactions. Here, we show explicitly that local mechanical interactions in biological systems may regulate the stability, the reversibility, and the cooperative/non-cooperative character of the debonding transition. We show that this transition is characterized by a single parameter depending on an internal length scale. Our theory describes a wide range of melting transitions found in biological systems such as protein secondary structures, microtubules and tau proteins, and DNA molecules. In these cases, the theory gives the critical force as a function of the chain length and its elastic properties. Our theoretical results provide quantitative predictions for known experimental effects that appear in different biological and biomedical fields.

Greenberger-Horne-Zeilinger states and few-body Hamiltonians.

The generation of Greenberger-Horne-Zeilinger (GHZ) states is a crucial problem in quantum information. We derive general conditions for obtaining GHZ states as eigenstates of a Hamiltonian. We find that a necessary condition for an n-qubit GHZ state to be a nondegenerate eigenstate of a Hamiltonian is the presence of m-qubit couplings with m≥[(n+1)/2]. Moreover, we introduce a Hamiltonian with a GHZ eigenstate and derive sufficient conditions for the removal of the degeneracy.

A coarse-grained mechanical model for folding and unfolding of tropoelastin with possible mutations.

We propose a simple general framework to predict folding, native states, energy barriers, protein unfolding, as well as mutation induced diseases and other protein structural analyses. The model should not be considered as an alternative to classical approaches (Molecular Dynamics or Monte Carlo) because it neglects low scale details and rather focuses on global features of proteins and structural information. We aim at the description of phenomena that are out of the range of classical molecular modeling approaches due to the large computational cost: multimolecular interactions, cyclic behavior under variable external interactions, and similar. To demonstrate the effectiveness of the approach in a real case, we focus on the folding and unfolding behavior of tropoelastin and its mutations. Specifically, we derive a discrete mechanical model whose structure is deduced based on a coarse graining approach that allows us to group the amino acids sequence in a smaller number of `equivalent' masses. Nearest neighbor energy terms are then introduced to reproduce the interaction of such amino acid groups. Nearest and non-nearest neighbor energy terms, inter and intra functional blocks are phenomenologically added in the form of Morse potentials. As we show, the resulting system reproduces important properties of the folding-unfolding mechanical response, including the monotonic and cyclic force-elongation behavior, representing a physiologically important information for elastin. The comparison with the experimental behavior of mutated tropoelastin confirms the predictivity of the model. STATEMENT OF SIGNIFICANCE: Classical approaches to the study of phenomena at the molecular scale such as Molecular Dynamics (MD) represent an incredible tool to unveil mechanical and conformational properties of macromolecules, in particular for biological and medical applications. On the other hand, due to the computational cost, the time and spatial scales are limited. Focusing of the real case of tropoelastin, we propose a new approach based on a careful coarse graining of the system, able to describe the overall properties of the macromolecule and amenable of extension to larger scale effects (protein bundles, protein-protein interactions, cyclic loading). The comparison with tropoelastin behavior, also for mutations, is very promising.

Diagnosis of deep infiltrating endometriosis: accuracy of magnetic resonance imaging and transvaginal 3D ultrasonography.

PURPOSE: To compare two different imaging modalities, magnetic resonance (MR), and three-dimensional sonography (3DUS), in order to evaluate the specific role in preoperative work-up of deep infiltrating endometriosis. MATERIALS AND METHODS: 33 women with endometriosis underwent 3DUS and MR followed by surgical and histopathological investigations. Investigators described the disease extension in the following sites: torus uterinus and uterosacral ligaments (USL), vagina, rectovaginal-septum, rectosigmoid, bladder, ovaries. Results were compared with surgical and histopathological findings. RESULTS: Ovarian and deep pelvic endometriosis were found by surgery and histology in, respectively, 24 (72.7%) and 22 (66.6%) of the 33 patients. Sensitivity and specificity values of 3DUS for the diagnosis of endometrial cysts were 87.5% and 100%, respectively; those of MRI were 96.8% and 91.1%, respectively. Sensitivity and specificity of 3DUS for the diagnosis of deep infiltrating endometriosis in specific sites were: USL 50% and 94.7%; vagina 84% and 80%; rectovaginal-septum 76.9% and 100%; rectosigmoid 33.3% and 100%; bladder 25% and 100%. Those of MR were: USL 69.2% and 94.3%; vagina 83.3% and 88.8%; rectovaginal-septum 76.4% and 100%; restosigmoid 75% and 100%; bladder 83.3% and 100%. CONCLUSIONS: MR accurately diagnoses deep infiltrating endometriosis; 3DUS accurately diagnoses deep infiltrating endometriosis in specific locations.

Assessing the risk of laparoscopic morcellation of occult uterine sarcomas during hysterectomy and myomectomy: Literature review and the ISGE recommendations.

OBJECTIVE: This project of the International Society for Gynecologic Endoscopy (ISGE) had the objective to review the literature and provide recommendations on the occult sarcoma risk assessment in patients who are candidates for minimally invasive gynecological surgery involving intra-abdominal electromechanical tissue morcellation. STUDY DESIGN: The ISGE Task Force for Estimation of the Risk in Endoscopic Morcellation initially defined key topics and clinical questions which may guide a comprehensive preoperative patient assessment. A literature search within the Medline/PubMed and Cochrane Database was carried out using keywords "morcellation", "uterine fibroids", "uterine sarcoma", "myomectomy" and "hysterectomy". Relevant publications (original studies, meta-analyses and previous reviews), written in English and published until May 30th, 2017, were selected and analyzed. Previously emitted statements of 12 recognized professional societies or government institutions and their supporting literature were also studied. For each topic/clinical question, the available information was graded by the level of evidence. The ISGE recommendations were established in accordance with the evidence quality. RESULTS: In the light of available information, 9 recommendations on preoperative clinical, laboratorial and imaging evaluation of the candidates for intracorporeal uterus/leiomyoma morcellation were formulated, mainly based on consensus and expert opinions. There is a lack of high-quality evidence, which does not allow the establishment of strong recommendations. CONCLUSION: Electromechanical tissue morcellation may be used in gynecological patients who are considered "low risk" upon appropriate preoperative evaluation; however, further studies and prospective data collection are greatly needed to improve sarcoma risk assessment in women with presumed uterine leiomyomas.

Developments in techniques for laparoscopic myomectomy.

OBJECTIVES: Conflicting opinions about laparoscopic myomectomy (LM) are still present regarding indications and risks related to reproductive outcome. We reviewed our 13-year experience (1) to identify risk factors or changes in methods that have improved our myomectomy technique and (2) to evaluate how the learning curve and improved surgical devices influenced our procedures, and (3) to study the myomectomy scar with a power color Doppler ultrasound (US). METHODS: From January 1991 to December 2003, we studied 332 patients who underwent laparoscopic myomectomy. We analyzed, as the learning curve, how the introduction of the Steiner morcellator, the use of vasoconstrictive agents, and different techniques of suturing have influenced parameters such as operating time and blood loss. RESULTS: We performed 332 single or multiple myomectomies for symptomatic myomas. Most patients (47%) had more than one myoma, with a maximum of 8 per patient (average myomas removed for patients: 2.23, range 1 to 8). Myoma size ranged from 1cm to 20 cm (mean, 60.20+/-SD27.1 mm). Myomas <4cm were removed during myomectomy for larger ones. The conversion rate to laparotomy was 1.51%. The average drop in hemoglobin concentration was 1.06+/-SD0.86 g/100 mL (range, 0.7 to 2.2 g/100 mL). No blood transfusions were required. No major intraoperative complications occurred. The duration of the procedure ranged from 30 minutes to 360 minutes (mean, 124+/-SD52.6). The dimensions of the myomas removed increased with experience (4.91+/-SD2.2 cm of the earlier cases to 6.76+/-SD2.7 of the latest group, P<0.000). The learning curve positively influenced the length of the procedures in the first cases. The introduction of electromechanical morcellation in 1996 reduced the procedure time. Data showed significantly reduced Hb drop after the introduction in 1998 of vasoconstrictive agents (DeltaHb 1.62 g/100 mL versus 0.95; P<0.001). The running suture offered few advantages in terms of procedure time. However, the drop in hemoglobin was advantageous (DeltaHb 1.1 g/100mL vs 0.61, P<0.01). The overall rate of intrauterine pregnancy following LM was 65.5%. No uterine ruptures occurred. We had 2 serious postoperative complications. CONCLUSION: With increased experience, the technical improvements and clinical results have changed our approach and decision making regarding laparoscopic myomectomy. Our results and extremely low conversion rate suggest that laparoscopic myomectomy is a safe and reliable procedure even in the presence of multiple or enlarged myomas.