Tethering Point Research Articles

Ipsilateral Nasoseptal Flaps in a Transpterygoid Approach: Technical Pearls and Reconstruction Outcomes

Abstract Background Transpterygoid approaches to the skull base require dissection of the sphenopalatine artery, potentially compromising the option to harvest an ipsilateral nasoseptal flap (NSF) for reconstruction. In cases where other reconstructive options are limited, it may be necessary to utilize a NSF ipsilateral to the transpterygoid approach. Here, we describe the technique of NSF pedicle preservation with reconstruction outcomes. Methods This was a retrospective single-institution review of all expanded endonasal skull base cases utilizing a NSF ipsilateral to a transpterygoid approach. Reconstruction outcomes collected include intraoperative fluorescence with indocyanine green (ICG), postoperative magnetic resonance imaging (MRI) gadolinium enhancement, endoscopic assessment, and reconstruction-related complications. Results Twenty-one cases were included in this study (mean age 51.0 ± 20.6 years, 61.9% female). Indications for NSF ipsilateral to the transpterygoid approach included: bilateral transpterygoid approach (52.4%), revision reconstruction (23.8%), or significant septal deviation (19.0%). Twelve of 14 (85.7%) flaps demonstrated intraoperative perfusion with ICG, 15 of 15 (100%) enhanced on postoperative MRI, and 21 of 21 (100%) flaps had a healthy, viable appearance on postoperative endoscopy. There were no instances of flap necrosis or postoperative cerebrospinal fluid leaks. Technical keys to optimize mobilization of the pedicle include wide decompression of the sphenopalatine foramen and release of neurovascular tethering points of the pterygopalatine fossa. These steps allow for wide skull base exposure with preservation of the sphenopalatine artery. Conclusion With this technique, the transpterygoid approach can be performed in a manner that preserves the pedicle for an ipsilateral NSF and achieve an excellent reconstructive outcome.

The Mastoid Crevasse and 3-Dimensional Considerations in Deep Plane Neck Lifting.

Advances in face and neck lifting involve release of tethering points along the superficial musculoaponeurotic system-platysma complex to freely manipulate the deep natural glide plane in the face and neck. The aim of this article was to determine a combination of deep plane techniques for addressing the face and neck and to elucidate, for the first time, a measurable endpoint for the gonial angle. Analysis of deep plane tethering and decussation zones was also undertaken. Extended deep plane surgery performed in 79 patients (158 hemifaces; age, 30-75 years; 95% female), over a 3-month period, was reviewed. Patients were followed for 1 year. Measurements were performed systematically during deep plane face and neck lifting. Before intervention, the mean [standard deviation] gonial depth was 9.4 [3.6] mm on the left and 8.3 [2.7] mm on the right. The mean depth created below the gonial angle when measuring the traditional suspension to the anterior mastoid was 15.8 [3.3] mm on the left and 13.7 [2.5] mm on the right. The distance postoperatively when measuring the gonial depth after performing the crevasse technique was 23.2 [2.2] mm on the left and 22.5 [2.5] mm on the right. This represents a mean increase in the advancement of 7.4 mm on the left and 8.8 mm on the right (average, 8.1 mm) which was demonstrated to be statistically significant bilaterally (P < .0001). The deep plane techniques described here aid manipulation of the deep plane and deep neck space, while also providing measurable endpoints and more effective modes of fixation by utilizing the mastoid crevasse. The use of techniques that release tension and allow redrape produce the most natural and well-balanced results.

Structural Preferences Shape the Entropic Force of Disordered Protein Ensembles.

Intrinsically disordered protein regions (IDRs) make up over 30% of the human proteome and exist in a dynamic conformational ensemble instead of a native, well-folded structure. Tethering IDRs to a surface (for example, the surface of a well-folded region of the same protein) can reduce the number of accessible conformations in these ensembles. This reduces the ensemble's conformational entropy, generating an effective entropic force that pulls away from the point of tethering. Recent experimental work has shown that this entropic force causes measurable, physiologically relevant changes to protein function. But how the magnitude of this force depends on IDR sequence remains unexplored. Here, we use all-atom simulations to analyze how structural preferences in IDR ensembles contribute to the entropic force they exert upon tethering. We show that sequence-encoded structural preferences play an important role in determining the magnitude of this force: compact, spherical ensembles generate an entropic force that can be several times higher than more extended ensembles. We further show that changes in the surrounding solution's chemistry can modulate the IDR entropic force strength. We propose that the entropic force is a sequence-dependent, environmentally tunable property of terminal IDR sequences.

Structural preferences modulate the entropic force exerted by disordered proteins.

When tethered to surfaces such as lipid vesicles or well-folded proteins, polymers exert an entropic force that pulls against the point of tethering. This is because the motions produced by the protein's thermal fluctuations push against and away from the tethered surface. Intrinsically disordered protein regions (IDRs) commonly exist at the termini of proteins. When tethered to protein or membrane surfaces, IDRs were shown to exert an entropic force that is thought to largely depend on their length. However, IDPs are not homopolymers: their sequences can be complex and their conformational ensembles have structural preferences that will affect their average shape. We hypothesize that such IDR structural preferences also affect the entropic force exerted by the sequence. To test this hypothesis, we use all-atom simulations and an enhanced sampling strategy to quantify the entropic force exerted by over 100 IDR sequences. We find that IDRs with compact ensembles tend to induce a stronger entropic force than expanded IDRs. We also find that solution condition changes will alter IDR ensemble structure and thus alter the magnitude of the entropic force. Our work indicates that the structural preferences of IDRs, coupled with their interaction with the solution condition, can act together to dramatically increase the entropic force of some, but not all, IDRs.

In situ activation of green sorbents for CO2 capture upon end group backbiting.

Thermolysis of a urethane end group was observed as a first time phenomenon during activation. This unzipping mechanism revealed a new amine tethering point producing a diamine-terminated oligourea ([10]-OU), acting as a green sorbent for CO2 capturing. The oligomer backbites its end group to form propylene carbonate (PC), as proved by in situ TGA-MS, which can reflect the polymer performance by maximizing its capturing capacity. Cross polarization magic angle spinning (CP-MAS) NMR spectroscopy verified the formation of the proven ionic carbamate (1:2 mechanism) with a chemical shift at 161.7 ppm due to activation desorption at higher temperatures, viz., 100 °C (in vacuo) accompanied with bicarbonate ions (1:1 mechanism) with a peak centered at 164.9 ppm. Fortunately, the amines formed from in situ thermolysis explain the abnormal behavior (carbamates versus bicarbonates) of the prepared sample. Finally, ex situ ATR-FTIR proved the decomposition of urethanes, which can be confirmed by the disappearance of the pre-assigned peak centered at 1691 cm-1. DFT calculations supported the thermolysis of the urethane end group at elevated temperatures, and provided structural insights into the formed products.

Carbon Nanotubes, Graphene, and Carbon Dots as Electrochemical Biosensing Composites.

Carbon nanomaterials (CNMs) have been extensively used as electrochemical sensing composites due to their interesting chemical, electronic, and mechanical properties giving rise to increased performance. Due to these materials’ unknown long-term ecological fate, care must be given to make their use tractable. In this review, the design and use of carbon nanotubes (CNTs), graphene, and carbon dots (CDs) as electrochemical sensing electrocatalysts applied to the working electrode surface are surveyed for various biosensing applications. Graphene and CDs are readily biodegradable as compared to CNTs. Design elements for CNTs that carry over to graphene and CDs include Coulombic attraction of components and using O or N atoms that serve as tethering points for attaching electrocatalytically active nanoparticles (NPs) and/or other additives.

Grading of "Back Rolls": Guide to Treatment Options.

“Back Rolls,” as the term indicates, are basically fat deposits on the back in the form of rolls. This is a common deformity in women, and concerns were encountered by cosmetic surgeons the world over, especially in patients with massive weight loss due to diet or bariatric surgery and who would like to wear a form hugging costume. The skin–fat envelope of the back normally adheres tightly to the underlying musculoskeletal anatomy of the rib cage. This envelope is held in place by facial attachments that are akin to the “zones of adherence” described by Rohrich et al.1 The extent of fat deposits and number of back rolls, as well as skin laxicity, varies from person to person and also from one side to the other. The rolls surely have a zone of adherence inferiorly over which the tissue fold hangs and medially in the midline. Treatment modalities for back rolls depend on the above-mentioned variables and involve three general approaches: Injection lipolysis in association with weight loss2; Ultrasound-assisted lipectomy with or without skin tightening3; Direct surgical excision of the skin fold4 as an upper back lift. The choice of treatment depends on the specific characteristic of the back roll; hence, a classification to grade the extent of back roll would help in guiding the surgeon to choose the best possible option. Fat deposits in the saddle bag area, abdomen, chest, and submental area have been classified clinically to guide the treatment modality, but unfortunately, we have not come across any published classification system (whether anatomical or clinical) to categorize back rolls. After retrospectively going through the photographs and surgical details of more than 1800 Indian women who have undergone back contouring in the last 17 years, we propose the following classification for categorizing back rolls (Fig. 1):Fig. 1.: Grading of back rolls as seen clinically. A, Left side shows Grade II back roll with a single incomplete indentation, whereas the right side (Grade III) shows two indentations: the lower is complete, whereas the upper is incomplete. Please note that the maximum protrusion of skin fold (yellow arrow) is higher than the inferior indentation (black arrow). B, Grade IV back roll. The maximum protrusion of skin fold (yellow arrow) is lower than the inferior indentation (black arrow). Grade I: Back rolls that appear when the arms are kept by the side and disappear when the arms are raised. Grade II: Back rolls having a single indentation (partial or complete) that reduces when the arm is raised. Grade III: Back rolls with two or more skin indentations with skin pinch of more than 2 cm. The skin fold should not be lower than the inferior tethering point. Grade IV: Back rolls secondary to massive weight loss that have multiple folds with skin pinch less than 2 cm and skin fold lower than the tethering point, or in patients who have undergone prior surgical treatment. A lack of a comprehensive and clinically appropriate classification system prevents an accurate diagnosis, limits the use of treatment algorithm, and makes it difficult to compare treatment outcomes. We believe that this categorization can be used to guide the most appropriate treatment modality for a specific type of back roll that would be ideal. Additional studies are required to validate this classification system in other parts of the world. DISCLOSURE The authors have no financial interest to declare in relation to the content of this article. No funding has been received for this study.

Equilibrium folding and unfolding dynamics to reveal detailed free energy landscape of src SH3 protein by magnetic tweezers* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11874309 and 11474237) and the 111 Project (Grant No. B16029).

Src SH3 protein domain is a typical two-state protein which has been confirmed by research of denaturant-induced unfolding dynamics. Force spectroscopy experiments by optical tweezers and atomic force microscopy have measured the force-dependent unfolding rates with different kinds of pulling geometry. However, the equilibrium folding and unfolding dynamics at constant forces has not been reported. Here, using stable magnetic tweezers, we performed equilibrium folding and unfolding dynamic measurement and force-jump measurement of src SH3 domain with tethering points at its N- and C-termini. From the obtained force-dependent transition rates, a detailed two-state free energy landscape of src SH3 protein is constructed with quantitative information of folding free energy, transition state barrier height and position, which exemplifies the capability of magnetic tweezers to study protein folding and unfolding dynamics.

Theoretical and Experimental Design of Heavy Metal-Mopping Magnetic Nanoparticles.

Herein, we show a comprehensive experimental, theoretical, and computational study aimed at designing macromolecules able to adsorb a cargo at the nanoscale. Specifically, we focus on the adsorption properties of star diblock copolymers, i.e., macromolecules made by a number f of H-T diblock copolymer arms tethered on a central core; the H monomeric heads, which are closer to the tethering point, are attractive toward a specific target, while the T monomeric tails are neutral to the cargo. Experimentally, we exploited the adaptability of poly(2-oxazoline)s (POxs) to realize block copolymer-coated nanoparticles with a proper functionalization able to interact with heavy metals and show or exhibit a thermoresponsive behavior in aqueous solution. We here present the synthesis and analysis of the properties of a high molecular mass block copolymer featured by (i) a polar side chain, capable of exploiting electrostatic and hydrophilic interaction with a predetermined cargo, and (ii) a thermoresponsive scaffold, able to change the interaction with the media by tuning the temperature. Afterward, the obtained polymers were grafted onto iron oxide nanoparticles and the thermoresponsive properties were investigated. Through isothermal titration calorimetry, we then analyzed the adsorption properties of the synthesized superparamagnetic nanoparticles for heavy metal ions in aqueous solution. Additionally, we use a combination of scaling theories and simulations to link equilibrium properties of the system to a prediction of the loading properties as a function of size ratio and effective interactions between the considered species. The comparison between experimental results on adsorption and theoretical prediction validates the whole design process.

Molecular simulation of polymer crystallization under chain and space confinement.

Polymer crystallization under chain and space confinements is studied by Monte Carlo simulation. The simulation results show that the crystallinity and melting temperature of confined systems increase with the increase of free chain content. Furthermore, the crystallinity and melting temperature of confined systems with larger lateral size are higher than those with smaller lateral size. These findings are in good agreement with the conclusions obtained in some experiments. An important phenomenon that cannot be observed in experiments has been confirmed, that is, the tethering point can be used as the nucleation site. For the confined polymer system with the lateral size of 8 lattice points, with the increase of free chain content, the surface free energy of the nuclei and the diffusion activation energy of the chains decrease due to the combined effects of chain conformation size and chain movement ability, which leads to the enhancement of the nucleation ability of polymers. However, for the confined polymer system with lateral size of 12 lattice points, with the increase of free chain content, the nucleation sites decrease and the critical free energy barrier increases, which are not conducive to nucleation. Moreover, the existence of interfacial interactions can also significantly change the crystallization of confined polymers. Our results indicate the crystallization kinetics of the confined polymer from a microscopic point of view.

Critiquing the Conception of "Crimes Against Nature": The Necessity for a New "Natural" Law.

Drawing upon historical developments and legal interpretations of "crimes against nature" as it relates to bestiality, this paper endeavors to promote further discussions surrounding the conception of "natural" and/or extant law, by which an understanding of historical and modern objections to crimes against nature opens them up to the critique of thin-universalism-that is, that despite disparate socio-moral fundaments, laws of prohibition coalesce around evangelical totalities. We contend that a paradigm shift in respect of naturalness is necessitated-naturalness should be packaged and represented, in part, by the empirical. Thus, conceptions of vulnerability and sentience rooted in social scientific understandings and in hospitable forms of rights protections ought to provide a new understanding of governance of the natural. In turn, this naturalness ought to be reflected in law so long as the boundaries we propose are not unduly transgressed. If unnatural acts like bestiality have their prohibitions in the legal tethering points of Judeo-Christian and, later Victorian roots, the new natural law ought to be apprised of rights-based constitutionalism and informed by green criminological and animal rights logics. Law, apprised of these ethics, would evolve to expand protections for animals, human and non-human alike. Laws based on the new naturalness could protect species and environments as evidence demands.

Fabrication of 2D Block Copolymer Brushes via a Polymer-Single-Crystal-Assisted-Grafting-to Method.

Block copolymer brushes are of great interest due to their rich phase behavior and value-added properties compared to homopolymer brushes. Traditional synthesis involves grafting-to and grafting-from methods. In this work, a recently developed "polymer-single-crystal-assisted-grafting-to" method is applied for the preparation of block copolymer brushes on flat glass surfaces. Triblock copolymer poly(ethylene oxide)-b-poly(l-lactide)-b-poly(3-(triethoxysilyl)propyl methacrylate) (PEO-b-PLLA-b-PTESPMA) is synthesized with PLLA as the brush morphology-directing component and PTESPMA as the anchoring block. PEO-b-PLLA block copolymer brushes are obtained by chemical grafting of the triblock copolymer single crystals onto a glass surface. The tethering point and overall brush pattern are determined by the single crystal morphology. The grafting density is calculated to be ≈0.36 nm-2 from the atomic force microscopy results and is consistent with the theoretic calculation based on the PLLA crystalline lattice. This work provides a new strategy to synthesize well-defined block copolymer brushes.

Placement of Tyrosine Residues as a Design Element for Tuning the Phase Transition of Elastin-peptide-containing Conjugates: Experiments and Simulations.

Elastin-like polypeptides (ELP) have been widely used in the biomaterials community due to their controllable, thermoresponsive properties and biocompatibility. Motivated by our previous work on the effect of tryptophan (W) substitutions on the LCST-like transitions of short ELPs, we studied a series of short ELPs containing tyrosine (Y) and/or phenylalanine (F) guest residues with only 5 or 6 pentapeptide repeat units. A combination of experiments and molecular dynamics (MD) simulations illustrated that the substitution of F with Y guest residues impacted the transition temperature (Tt) of short ELPs when conjugated to collagen-like-peptides (CLP), with a reduction in the transition temperature observed only after substitution of at least two residues. Placement of the Y residues near the N-terminal end of the ELP, away from the tethering point to the CLP, resulted in a lower Tt than that observed for peptides with the Y residues near the tethering point. Atomistic and coarse-grained MD simulations indicated an increase in intra- and inter- peptide hydrogen bonds in systems containing Y guest residues that are suggested to enhance the ability of the peptides to coacervate, with a concomitantly lower Tt. Simulations also revealed that the placement of Y-containing pentads near the N-terminus (i.e., away from CLP tethering point) versus C-terminus of the ELP led to more π-π stacking interactions at low temperatures, in agreement with our experimental observations of a lower Tt. Overall, this study provides mechanistic insights into the driving forces for the LCST-like transitions of ELPs and offers additional means for tuning the Tt of short ELPs for biomedical applications such as on-demand drug delivery and tissue engineering.

The Greater Occipital Nerve and Obliquus Capitis Inferior Muscle: Anatomical Interactions and Implications for Occipital Pain Syndromes.

The compression/injury of the greater occipital nerve has been identified as a trigger of occipital headaches. Several compression points have been described, but the morphology of the myofascial unit between the greater occipital nerve and the obliquus capitis inferior muscle has not been studied yet. Twenty fresh cadaveric heads were dissected, and the greater occipital nerve was tracked from its emergence to its passage around the obliquus capitis inferior. The intersection point between the greater occipital nerve and the obliquus capitis inferior, and the length and thickness of the obliquus capitis inferior, were measured. In addition, the nature of the interaction and whether the nerve passed through the muscle were also noted. All nerves passed either around the muscle loosely (type I), incorporated in the dense superficial muscle fascia (type II), or directly through a myofascial sleeve within the muscle (type III). The obliquus capitis inferior length was 5.60 ± 0.46 cm. The intersection point between the obliquus capitis inferior and the greater occipital nerve was 6.80 ± 0.68 cm caudal to the occiput and 3.56 ± 0.36 cm lateral to the midline. The thickness of the muscle at its intersection with the greater occipital nerve was 1.20 ± 0.25 cm. Loose, tight, and intramuscular connections were found in seven, 31, and two specimens, respectively. The obliquus capitis inferior remains relatively immobile during traumatic events, like whiplash injuries, placing strain as a tethering point on the greater occipital nerve. Better understanding of the anatomical relationship between the greater occipital nerve and the obliquus capitis inferior can be clinically useful in cases of posttraumatic occipital headaches for diagnostic and operative planning purposes.

How Tethered Probes Report the Dynamics of a Polymer near the Glass Transition.

How tethered probes report dynamics of host polymers near the glass transition was investigated by changing the length of the flexible linkers and the number of tethering points via imaging rotational fluorescence correlation microscopy and compared with free probes of different sizes. The results show that tethering did not alter the temperature-dependence of polymer dynamics and the shape of the correlation decay reported by the probe; however, the rotation slowed down up to ≈1 decade when both ends of the probe were restricted with short alkyl chain linkers. Upon comparison with the bigger free probe, the mechanism of the slowdown was attributed to the restricted motion upon tethering for tethered probes compared to averaging over different regions of the dynamic heterogeneity for the bigger probe. If the size of the probe was comparable to that of the dynamic heterogeneity of the system, tethered probes accurately report dynamics relevant to glass transition, regardless of tethering conditions.

Cardiac Microtissue Platform with Dynamically Tunable Afterload Control to Show Contractile Reserve and Pathologic Hypertrophy

Introduction Increased afterload induces structural and functional changes in the myocardium that ultimately lead to heart failure. Our lab uses engineered cardiac microtissues, composed of a well with two cantilevers that serve as tethering points for the tissue to model myocardium. We have created a platform with dynamically tunable in vitro afterload (cantilever stiffness) to study hypertrophy. We hypothesized that an instantaneous increase in stiffness will reveal contractile reserve, resulting in increased force, work, contraction velocity, and relaxation velocity. We also hypothesized that prolonged increases in stiffness will induce pathologic hypertrophy, showing decreases in these parameters. Methods and Results We used iron-doped polydimethylsiloxane to create cantilevers that stiffen in a magnetic field. After seeding a mixture of fibroblasts, cardiomyocytes, and collagen matrix, cardiac microtissues were matured over 48 hours, after which baseline testing was performed. Cardiac microtissues were then exposed to low or high stiffness conditions ( 0.6 N/m) for 48 hours and tested at 24 and 48 hours with and without a magnetic field. At baseline, an instantaneous 12.0% increase in stiffness (95% CI 9.4 - 14.6) caused a 13.0% increase in force development (95% CI 6.8 - 19.1) and a 14.8% increase in work (95% CI 1.7 - 28.0). At 24 hours, tissues exposed to high stiffness had significantly decreased work (92.2 vs. 50.6 μN*μm, p = 0.02), contraction velocity (-86.9 vs. -50.9 μm/s, p = 0.0002), and relaxation velocity (49.6 vs. 31.0 μm/s, p = 0.0003), with no significant change in force (31.1 vs. 26.7 μN, p = 0.26). Tissues exposed to high stiffness at 48 hours had significantly decreased work (81.2 vs. 44.4 μN*μm, p = 0.03), contraction velocity (-86.6 vs. -52.9 μm/s, p Conclusions Our data indicates that instantaneous exposure to increased afterload reveals contractile reserve, while sustained increased afterload induces pathologic changes in cardiac microtissues. The addition of dynamically tunable afterload to a cardiac microtissue model provides a variety of new opportunities to study load-dependent myocardial adaptations for translational research applications.

Shear-Induced Extensional Response Behaviors of Tethered von Willebrand Factor

We perform single-molecule flow experiments using confocal microscopy and a microfluidic device for shear rates up to 20,000 s−1 and present results for the shear-induced unraveling and elongation of tethered von Willebrand factor (VWF) multimers. Further, we employ companion Brownian dynamics simulations to help explain details of our experimental observations using a parameterized coarse-grained model of VWF. We show that global conformational changes of tethered VWF can be accurately captured using a relatively simple mechanical model. Good agreement is found between experimental results and computational predictions for the threshold shear rate of extension, existence of nonhomogenous fluorescence distributions along unraveled multimer contours, and large variations in extensional response behaviors. Brownian dynamics simulations reveal the strong influence of varying chain length, tethering point location, and number of tethering locations on the underlying unraveling response. Through a complex molecule like VWF that naturally adopts a wide distribution of molecular size and has multiple binding sites within each molecule, this work demonstrates the power of tandem experiment and simulation for understanding flow-induced changes in biomechanical state and global conformation of macromolecules.

Efficient Delivery of Plasmid DNA Using Incorporated Nucleotides for Precise Conjugation of Targeted Nanoparticles.

Many obstacles restrict development of DNA plasmid-based therapeutic delivery, involving but not limited to poor cellular uptake, premature material dissociation, and inefficient response. Additionally, lack of precision loading of the plasmids on the carrier nanoparticle may affect the overall nonspecificity in terms of loading as well as the site of loading. Here we report a strategy using the incorporation of a biotin-modified nucleotide into a 4.7 kb plasmid sequence for the site-specific nanoparticle conjugation as an improvement on targeted DNA plasmid delivery. Initially, a designed 80-nucleotide sequence was elongated by incorporating biotin-16-aminoallyl-2'-dCTP that facilitated streptavidin binding as determined via polyacrylamide gel electrophoresis (PAGE). This modified sequence was ligated into a specific location of the EGFP plasmid to avoid possible interference with important functional elements and gene expression off of the plasmid. In parallel, a gold nanoparticle complex comprising of either a CD44 or mutant DNA conjugated aptamer, a PEGylated streptavidin, and a derivatized hyaluronic acid stabilizing polymer was synthesized. To delineate the ability of this nanoparticle-plasmid complex to exhibit an improved cellular delivery, MDA-MB-231 cells were treated with a set of plasmid and plasmid-nanoparticle complexes. Successful expression of EGFP was only observed in cells treated with the biotin-modified EGFP plasmid and a streptavidin-CD44 aptamer-nanoparticle. This demonstrated the need for the specific biotin-streptavidin binding to avoid nanoparticle-plasmid dissociation for improved efficacy. This proof-of-principle concept creates a flexible scaffold that can be assimilated into any plasmid and can produce small RNAs or encoding a therapeutic gene via an installation of a design that uses incorporated modified nucleotides as tethering points for nanoparticles which can play host to stabilizing ligands, additional therapeutic molecules and antibody conjugates among other possibilities. In our system, the nanoparticles are vehicles for the addition of targeting ligands that were essential for cell specificity and enhanced cellular uptake.

The JAVA Based Computational Tool for Pairwise Comparison of Protein Backbone Folds in Liganded and Apo 3D Structures of the alpha/beta Hydrolase Fold Proteins

Cholinesterases, carboxylesterases and lipases are some of prominent catalytically active proteins with specifically similar, globular tertiary structure fold termed “alpha/beta hydrolase fold”. Ligand binding, both reversible and covalent, frequently results in small, yet systematic and potentially functionally important changes in the conformation of their alpha carbon backbones that can be easily overseen by commonly used overlays based on overall minimization of backbone atom RMSD analysis. In particular, backbone conformations of cholinesterases ‐ acetylcholinesterase and butyrylcholinesterase ‐ show only small conformational changes. This is revealed in more than 200 PDB deposited cholinesterase X‐ray structures in complexes with structurally diverse ligands that affect their function.We developed a novel, reference point based principle for overlay‐independent pairwise comparison of liganded and non‐liganded alpha carbon backbone conformations from respective PDB (Protein Data Bank) deposited 3D structure entries and encoded it in JAVA based computer algorithm for quick analysis. Comparisons are based on differences in distances between each alpha carbon and chosen reference point in each pair of compared structures, as well as on differences in the angle between center of mass, reference point and each of alpha carbons in the comparison. Combination of the two comparison criteria reveals subset of backbone alpha carbons in two structures that maintains best their relative positions in the 3D space and that can be used as tethering points for overlay of compared structures. Created overlay has capacity to reveal small but systematic local changes in the backbone conformation frequently masked by the overall RMSD minimization approach.Our systematic analysis of a number of PDB deposited alpha/beta hydrolase fold structures revealed small, yet functionally important conformational changes in their backbone consistent with experimental observations and instrumental in revealing molecular mechanisms in respective catalytic reactions. These findings are important for complete molecular target template characterization in the structure based development of novel antidotes of exposure to organophosphates which covalently inhibit this family of enzymes.Support or Funding InformationThis work was supported by the CounterACT Program, National Institutes of Health Office of the Director, Grant R21 NS098998 from NINDS.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effects of Chain Topology on the Self-Assembly of AB-Type Block Copolymers

The effects of chain topology on the self-assembly of block copolymers are examined using an ABAT block copolymer, composed of an AB diblock copolymer with an extra A block tethered onto the B block, as a model system. The topology of the ABAT block copolymer is regulated by the tethering point, such that the block copolymer changes continuously from linear ABA triblock copolymer to A2B miktoarm star copolymer as the tethering position moves from the B end to the AB junction. The phase diagrams of ABAT copolymers of different tethering positions are constructed using the self-consistent field theory. The theoretical results reveal that the phase behavior of the system depends sensitively on the topology of the ABAT copolymers. In particular, a considerably wide stable region of the perforated lamellar (PL) phase is predicted for ABAT with proper tethering positions. The PL phase could even completely replaces the gyroid phase at relatively strong segregation. Furthermore, a large window of the hexagonally...