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Dr. Robert  Engel  Dpm image

Dr. Robert Engel Dpm

1398 Victory Blvd
Staten Island NY 10301
718 814-4515
Medical School: Other - Unknown
Accepts Medicare: No
Participates In eRX: No
Participates In PQRS: No
Participates In EHR: No
License #: 003008
NPI: 1962503003
Taxonomy Codes:
213E00000X

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Publications

Cyclic phosphonium ionic liquids. - Beilstein journal of organic chemistry
Ionic liquids (ILs) incorporating cyclic phosphonium cations are a novel category of materials. We report here on the synthesis and characterization of four new cyclic phosphonium bis(trifluoromethylsulfonyl)amide ILs with aliphatic and aromatic pendant groups. In addition to the syntheses of these novel materials, we report on a comparison of their properties with their ammonium congeners. These exemplars are slightly less conductive and have slightly smaller self-diffusion coefficients than their cyclic ammonium congeners.
Dietary crystalline common-, micro-, nanoscale and emulsified nanoscale sitosterol reduce equally the cholesterol pool in guinea pigs, but varying nanosystems result in different sterol concentrations in serosal jejunum. - Nanomedicine : nanotechnology, biology, and medicine
Due to hypocholesterolemic effects, sitosterol is used in functional foods and nanoscale dispersions. To investigate the influence of dietary sitosterol on sterol concentrations in Dunkin Hartley guinea pigs, seven groups consisting of eight animals each were fed either a basal diet (BD), a high-cholesterol diet (HC) or a high-cholesterol diet supplemented with crystalline commonscale (CCS), microscale (CMS, low-dosed: CMLS), nanoscale (CNS) or emulsified nanoscale (ENS) sitosterol. When compared to HC group, all sitosterol formulations decreased liver cholesterol concentrations. No differences in cholesterol or sitosterol concentration were found in plasma and liver between CCS, CMS, CNS, and ENS groups. Apparent cholesterol digestibility decreased by increasing crystalline microscale sitosterol doses. Despite a lower sitosterol intake, ENS group had higher serosal sitosterol concentrations in jejunum than CNS group. To elucidate an impact of the sitosterol nanosystem on gut tissues further studies are necessary.In this study, the use of sitosterols in a rat model led to contradicting conclusions regarding their ability to reduce cholesterol levels efficiently in guinea pigs, suggesting that more preclinical data is needed before this method could become applicable to human studies.Copyright © 2013 Elsevier Inc. All rights reserved.
Efficient emulsification of viscous oils at high drop volume fraction. - Langmuir : the ACS journal of surfaces and colloids
It is shown experimentally in this study that the increase of drop volume fraction can be used as an efficient tool for emulsification of viscous oils in turbulent flow. In a systematic series of experiments, the effects of drop volume fraction and viscosity of the dispersed phase on the mean, d(32), and maximum, d(V95), diameters of the drops, formed during emulsification, are quantified. The volume fraction, Φ, of the dispersed oily phase is varied between 1% and 90%, and oils with viscosity varying between 3 and 10,000 mPa.s are studied. All experiments are performed at sufficiently high surfactant concentration, as to avoid possible drop-drop coalescence during emulsification. The analysis of the experimental data shows that there is a threshold drop volume fraction, Φ(TR), at which a transition from inertial turbulent regime into viscous turbulent regime of emulsification occurs, due to the increased overall viscosity of the emulsion. At Φ < Φ(TR), d(32) and d(V95) depend weakly on Φ and are well described by known theoretical expression for emulsification in inertial turbulent regime (Davies, Chem. Eng. Sci. 1985, 40, 839), which accounts for the effects of oil viscosity and interfacial tension. At Φ > Φ(TR), both d(32) and polydispersity of the formed emulsions decrease very significantly with the increase of Φ (for the oils with η(D) > 10 mPa.s). Thus, very efficient emulsification of the viscous oils is realized. Very surprisingly, a third regime of emulsification is observed in the range of concentrated emulsions with Φ > 75%, where the mean drop size and emulsion polydispersity are found experimentally to be very similar for all oils and surfactants studied-an experimental fact that does not comply with any of the existing models of drop breakup during emulsification. Possible mechanistic explanations of this result are discussed. The experimental data for semiconcentrated and concentrated emulsions with Φ > Φ(TR) are described by a simple scaling expression, which accounts for the effects of all main factors studied.© 2011 American Chemical Society
Polycationic glycosides. - Molecules (Basel, Switzerland)
Cationic lipids have long been known to serve as antibacterial and antifungal agents. Prior efforts with attachment of cationic lipids to carbohydrate-based surfaces have suggested the possibility that carbohydrate-attached cationic lipids might serve as antibacterial and antifungal pharmaceutical agents. Toward the understanding of this possibility, we have synthesized several series of cationic lipids attached to a variety of glycosides with the intent of generating antimicrobial agents that would meet the requirement for serving as a pharmaceutical agent, specifically that the agent be effective at a very low concentration as well as being biodegradable within the organism being treated. The initial results of our approach to this goal are presented.
Polycations. 17. Synthesis and properties of polycationic derivatives of carbohydrates. - Carbohydrate research
In our continuing investigation of polycationic salts for purposes of antimicrobial action, ion-channel blocking, and construction of ionic liquids, we have prepared several series of polycationic salts derived from carbohydrate precursors. These salts are currently being investigated for optimal efficacy as antibacterials and antifungals, as well as for other applications. The syntheses of such series of salts are described here along with preliminary antibacterial testing results and a discussion of their properties indicating their potential utility for several purposes.
Preparation of ionic liquid based solid-phase microextraction fiber and its application to forensic determination of methamphetamine and amphetamine in human urine. - Journal of chromatography. A
A new solid-phase microextraction (SPME) procedure using an ionic liquid (IL) has been developed. Reusable IL-based SPME fiber was prepared for the first time by fixing IL through cross-linkage of IL impregnated silicone elastomer on the surface of a fused silica fiber. 1-Ethoxyethyl-3-methylimidazloium bis(trifluoromethane) sulfonylimide ([EeMim][NTf(2)]) ionic liquid was employed as a demonstration and the prepared fiber was applied to the forensic headspace determination of methamphetamine (MAP) and amphetamine (AP) in human urine samples. Important extraction parameters including the concentration of salt and base in sample matrix, extraction temperature and extraction time were investigated and optimized. Combined with gas chromatography/mass spectrometry (GC/MS) working in selected ion monitoring (SIM) mode, the new method showed good linearity in the range of 20-1500 microg L(-1), good repeatability (RSD<7.5% for MAP, and <11.5% for AP, n=6), and low detection limits (0.1 microg L(-1) for MAP and 0.5 microg L(-1) for AP). Feasibility of the method was evaluated by analyzing human urine samples. Although IL-based SPME is still at the beginning of its development stage, the results obtained by this work showed that it is a promising simple, fast and sensitive sample preparation method.
Polycations. 19. The synthesis of symmetrical dicationic lipids with internal dimethylazonia functionalities separated by a spacer unit and pendant chains. - Chemistry and physics of lipids
Herein is reported the preparation of several series of symmetrical polyammonium salts that serve as cationic lipids or precursors thereof, and are structurally based on several series of parent diamines where dimethylazonia functionalities are present, separated by a central structural unit, and pendant terminal chains. The resultant materials are of significant interest for a variety of purposes, such as serving as antihydrophobic species and as transfectins, the details of which are provided in separate reports. Attempts to effect selective alkylation to provide the corresponding unsymmetrical cationic lipids were without success, always leading to relatively useless mixtures of products.
Polycations. 18. The synthesis of polycationic lipid materials based on the diamine 1,4-diazabicyclo[2.2.2]octane. - Chemistry and physics of lipids
Herein is reported the preparation of several series of polyammonium salts that serve as cationic lipids or precursors thereof, and are structurally based on the parent diamine 1,4-diazabicyclo[2.2.2]octane (dabco). Through selective alkylation of dabco a variety of di- and tetracationic lipid species and precursors thereof have been prepared. The resultant materials are of significant interest for a variety of purposes, including serving as antimicrobial agents and antihydrophobic species, the details of which are provided in separate reports.
1,4-Diazabicyclo[2.2.2]octane derivatives: a novel class of voltage-gated potassium channel blockers. - Molecular pharmacology
Voltage-gated potassium (Kv) channels are targets for therapeutic drugs in the treatment of pathologic conditions including cardiac arrhythmia and epilepsy. In this study, we synthesized three classes of novel polyammonium compounds incorporating the bicyclic unit 1,4-diazabicyclo[2.2.2]octane (DABCO) and tested their action on three representative mammalian Kv channels (Kv2.1, Kv3.4, and Kv4.2) expressed in Xenopus laevis oocytes. Nonsubstituted DABCO did not block the Kv channels tested. Simple DABCO monostrings and diDABCO strings inhibited Kv2.1 and Kv3.4 channels, with potency increasing with string length for both these DABCO classes. Both Kv2.1 and Kv3.4 were most sensitive to C16 monostrings, with IC50 values of 1.9 and 0.6 microM, respectively. For compounds comprising two DABCO groups separated by an aromatic ring, inhibition depended upon relative positioning of the two DABCO groups, and only the para form (JC638.2alpha) was active, blocking Kv2.1 with an IC50 of 186 microM. Kv4.2 channels were relatively insensitive to all compounds tested. Unlike the tetraethylammonium ion (TEA), neither JC638.2alpha nor C16 monostring TA279 produced block when applied intracellularly via the recording electrode to Kv2.1 channels expressed in Chinese hamster ovary cells, suggesting against an internal site of action. However, JC638.2alpha protected an introduced cysteine (K356C) in the Kv2.1 outer pore from permanent modification by methanethiosulfonate ethyltrimethylammonium (MTSET). These data suggest that JC638.2alpha occupies an external binding site similar to that of TEA in the Kv2.1 outer pore, but with much higher affinity than TEA. These DABCO salts represent a new class of Kv channel blockers, some with higher potencies than any previously described quaternary ammonium ions. The potential for synthesis of an array of modular derivatives suggests that DABCO compounds hold promise as probes of Kv channel structure and identity and as potential therapeutic agents.
Preparation and investigation of antibacterial carbohydrate-based surfaces. - Carbohydrate research
Surfaces bearing carbohydrate units have been modified in a two-step process to incorporate functionalities (lipophilic with polycationic units) that bear antibacterial activity. The effectiveness of these modified surfaces for antibacterial action against a series of seven Gram-positive and Gram-negative bacteria are reported.

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