Search results for "Cosine"
showing 10 items of 88 documents
Impact of Branching on the Solution Behavior and Serum Stability of Starlike Block Copolymers.
2019
The size control of nanomedicines for tumor diagnosis and therapy is of high importance, since it enables or disables deep and sufficient tumor penetration. Amphiphilic star-shaped block copolypept(o)ides offer substantial promise to precisely adjust the hydrophobic core and the hydrophilic corona, independent of each other, and therefore simultaneously control the size dimension in the interesting size range from 10 to 30 nm. To gain access to core-shell structures of such sizes, 3-arm and 6-arm PeptoStars, based on poly(gamma-tert-butyloxycarbonyl-L-glutamate)-b-polysarcosine (pGlu(OtBu)-b-pSar), were prepared via controlled living ring-opening polymerization (ROP) of the corresponding N-…
Novel Narrow-Band Spectral Interference Filter with Very High Transmittance
2011
We report a novel scheme to improve the effective transmission of a standard interference filter, and demonstrate over 97% passband transmission. Such high efficiency is critical for quantum information applications, e.g. high-efficiency single-photon generation utilizing parametric down-conversion. The scheme can also be modified to function with a tilted filter, thereby allowing tuning of the passband frequency. In addition, the tilted configuration creates an infinite number of consecutive reflections from and transmissions through the filter, further improving the net filter transmission. Because spectral interference filters are a key element in optical quantum information experiments …
Generalization of Canny–Deriche filter for detection of noisy exponential edge
2002
This paper presents a generalization of the Canny-Deriche filter for ramp edge detection with optimization criteria used by Canny (signal-to-noise ratio, localization, and suppression of false responses). Using techniques similar to those developed by Deriche, we derive a filter which maximizes the product of the first two criteria under the constraint of the last one. The result is an infinite length impulse response filter which leads to a stable third-order recursive implementation. Its performance shows an increase of the signal-to-noise ratio in the case of blurred and noisy images, compared to the results obtained from Deriche's filter.
Catalysis in glycine N-methyltransferase: testing the electrostatic stabilization and compression hypothesis.
2006
Glycine N-methyltransferase (GNMT) is an S-adenosyl-l-methionine dependent enzyme that catalyzes glycine transformation to sarcosine. Here, we present a hybrid quantum mechanics/molecular mechanics (QM/MM) computational study of the reaction compared to the counterpart process in water. The process takes place through an SN2 mechanism in both media with a transition state in which the transferring methyl group is placed in between the donor (SAM) and the acceptor (the amine group of glycine). Comparative analysis of structural, electrostatic, and electronic characteristics of the in-solution and enzymatic transition states allows us to get a deeper insight into the origins of the enzyme's c…
Towards sarcosine determination in urine for prostatic carcinoma detection
2019
Abstract Sarcosine, a potential biomarker for prostate cancer, can be detected in a solid state enzyme based biosensor using sarcosine oxidase, with particle immobilised reagents. A novel fusion protein of the fluorescent protein, mCherry, sarcosine oxidase (SOx), and the polypeptide R5 (R52-mCherry-SOx-R5-6 H), was explored, which allowed self-immobilization on silica microparticles and long-term (90 days +) retention of activity, even at room temperature. In contrast, commercial wildtype SOx lost activity in a few days. A silica-R52-mCherry-SOx-R5-6H microparticle sensor for determination of sarcosine in urine, linked the SOx coproduct, H2O2, to a measurement catalysed by horseradish pero…
A head-to-head comparison of poly(sarcosine) and poly(ethylene glycol) in peptidic, amphiphilic block copolymers
2015
Abstract In this work we compare chemical and solution properties, like critical aggregate concentrations (CAC) and hydrodynamic radii of aggregates based on either poly(ethylene glycol) or poly(sarcosine) block copolymers in aqueous solution. The amine functionalized, hydrophilic polymers poly(sarcosine) (degree of polymerization, X n = 100 and 200) and PEG (X n = 121 and 242) of comparable hydrodynamic volume were used to initiate the ring opening polymerization of α-amino acid- N -carboxyanhydrides based on ɣ-benzyl- l -glutamate (Glu(OBn)) or e-carboxybenzyl- l -lysine (Lys(Z)). The second, hydrophobic block was kept at a degree of polymerization of 25 and 50 to enable a direct compar…
Poly-sarcosine and poly(ethylene-glycol) interactions with proteins investigated using molecular dynamics simulations
2018
Nanoparticles coated with hydrophilic polymers often show a reduction in unspecific interactions with the biological environment, which improves their biocompatibility. The molecular determinants of this reduction are not very well understood yet, and their knowledge may help improving nanoparticle design. Here we address, using molecular dynamics simulations, the interactions of human serum albumin, the most abundant serum protein, with two promising hydrophilic polymers used for the coating of therapeutic nanoparticles, poly(ethylene-glycol) and poly-sarcosine. By simulating the protein immersed in a polymer-water mixture, we show that the two polymers have a very similar affinity for the…
Regio- and stereoselective synthesis of spiro-heterocycles bearing the pyrazole scaffold via [3+2] cycloaddition reaction
2022
Abstract Herein we reported the utility of one-pot multicomponent based [3+2] cycloaddition reaction transformation to prepare a new two hybrids of spirooxindoles engrafted with pyrazole skeleton. Upon treatment of the electron-deficient olefins based pyrazole motif with in situ the generated azomethine ylides (AY) of sarcosine with the 6-chloro-isatin afforded spiroadducts. To enlighten the regio- and diastereo-selectivity of these spiroheterocycles, single crystal X-ray diffraction analysis was presented. Using Hirshfeld calculations, many short distance contacts such as O…H, Cl…H, N…H, H…C, C…C and Cl…S have a great impact on the molecular packing and the crystal stability of 8a and 8b. …
Influence of Riboflavin Targeting on Tumor Accumulation and Internalization of Peptostar Based Drug Delivery Systems.
2020
Riboflavin carrier protein (RCP) and riboflavin transporters (RFVTs) have been reported to be highly overexpressed in various cancer cells. Hence, targeting RCP and RFVTs using riboflavin may enhance tumor accumulation and internalization of drug delivery systems. To test this hypothesis, butyl-based 3-arm peptostar polymers were synthesized consisting of a lysine core (10 units per arm) and a sarcosine shell (100 units per arm). The end groups of the arms and the core were successfully modified with riboflavin and the Cy-5.5 fluorescent dye, respectively. While in phosphate buffered saline the functionalized peptostars showed a bimodal behavior and formed supramolecular structures over tim…
Poly(sarcosine) surface modification imparts stealth-like properties to liposomes
2019
Circulation lifetime is a crucial parameter for a successful therapy with nanoparticles. Reduction and alteration of opsonization profiles by surface modification of nanoparticles is the main strategy to achieve this objective. In clinical settings, PEGylation is the most relevant strategy to enhance blood circulation, yet it has drawbacks, including hypersensitivity reactions in some patients treated with PEGylated nanoparticles, which fuel the search for alternative strategies. In this work, lipopolysarcosine derivatives (BA-pSar, bisalkyl polysarcosine) with precise chain lengths and low polydispersity indices are synthesized, characterized, and incorporated into the bilayer of preformed…