Peptide Structure and Analysis
Marco Chinol, Giovanni Paganelli in Radionuclide Peptide Cancer Therapy, 2016
The SPPS requires a well-solvated gel to allow the reactions to take place between reagents in the mobile phase, and functional groups on chains throughout the interior of a resin. The original resin was developed as a polystyrene polymer cross-linked with 1% of 1,3-divinylbenzene with a swelling capacity 3 fold in volume in N,N-dimethylformamide (DMF). A polyamide resin was introduced by Atherton and Sheppard (21) under the concept that the solid support and peptide backbone should be of comparable polarities. Recently, resins based on grafting of polyethylene glycol (PEG) to low cross-linked polystyrene were developed such as Tentagel (22) and PEG-PS resins (23), with a swelling capacity 5 fold in volume in DMF. More recently, resins based on cross-linked PEG have also been available such as PEGA (24) and CLERA resins (25) with a swelling capacity 11, and 6.5 fold in volume, respectively. Due to their excellent swelling property, Tentagel and PEGA resins have shown superior performance, especially on peptides with long and difficult sequences.
Drug Analysis of Protein Microspheres: From Pharmaceutical Preparation to In Vivo Fate
Neville Willmott, John Daly in Microspheres and Regional Cancer Therapy, 2020
The most commonly used analytical technique for the determination of FUra is HPLC. The chromophore of FUra is only of moderate strength; this is not a problem with regard to analysis of the drug in formulations. However, when applied to biological fluids many HPLC methods based on ultraviolet detection with chromatography on octadecyl silica gel have a relatively poor sensitivity of ±100 ng/ml. Improved extraction techniques in combination with the use of styrene-divinylbenzene polymeric columns and ion-pairing reagents have yielded HPLC-ultra-violet procedures with limits of detection down to 10 ng/ml.91–93 Extended “cleanup” procedures after extraction also improve sensitivity.94 An advantage of HPLC methods is that they can detect fluoropyrimidines, such as 5′-dFUrd and FUrd, which are not ideal compounds for analysis by gas chromatography. The highest sensitivities afforded by HPLC involve alkylation of FUra with a fluorescent reagent,95,96 and these procedures might be improved further by using column switching to remove excess derivatization reagent. A specialized technique with high sensitivity involves derivatization of FUra to enable chemiluminescence detection.97
Monographs of Topical Drugs that Have Caused Contact Allergy/Allergic Contact Dermatitis
Anton C. de Groot in Monographs in Contact Allergy, 2021
Nicotine is the primary and a highly toxic alkaloid in tobacco products. It binds stereo-selectively to nicotinic-cholinergic receptors on autonomic ganglia, the adrenal medulla, neuromuscular junctions and in the brain. Nicotine exerts two effects, a stimulant effect exerted at the locus coeruleus and a reward effect in the limbic system. Therefore, nicotine is a highly addictive substance. This agent also induces peripheral vasoconstriction, tachycardia and elevated blood pressure. Nicotine in inhalers and patches is indicated for the relief of nicotine withdrawal symptoms and as an aid to smoking cessation. In pharmaceutical products, both nicotine base and nicotine complexed with methacrylic acid polymer and divinylbenzene (nicotine polacrilex; CAS number 96055-45-7, EC number not available, molecular formula not available) may be employed (1).
The role of artificial cells in the fight against COVID-19: deliver vaccine, hemoperfusion removes toxic cytokines, nanobiotherapeutics lower free radicals and pCO2 and replenish blood supply
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2022
Thomas Ming Swi Chang
Hemoperfusion is now an accepted routine clinical use for the treatment of patients around the world. A 2017 book [27] by specialists around the world shows that this approach is being used extensively around the world. There are now at least 10 commercial devices around the world [28]. Each company has their own proprietary methods. There are variations in the type of adsorbent, membrane material and membrane thickness and as a result, they are different in effectiveness [28]. There is a new commercial hemoperfusion device (HA330) not included in the 2017 review that has been approved for emergency use for COVID-19 in China, Europe and Canada. This is based on the use of collodion membrane with novel adsorbent in the form of synthetic styrene divinylbenzene copolymers macroporous resin [29,30].
Design, synthesis and characterization of enzyme-analogue-built polymer catalysts as artificial hydrolases
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Divya Mathew, Benny Thomas, Karakkattu Subrahmanian Devaky
The first report on substrate analogue imprinted chymotrypsin mimic was announced by Leonhardt and Mosbach in 1987 [46]. Imidazole residues were employed to hydrolyze amino acid p-nitrophenyl esters. A pyridine derivative of the amino acid- picolinyl-N-Boc protected amino acid- was used as the substrate analogue template molecule. The functional monomer 5-vinylimidazole and the template picolinyl-N-Boc protected amino acid were coordinated by Co(II) ions using CoCl2.6H2O in the pre-polymerization step. Then on copolymerization in presence of the crosslinker divinylbenzene (DVB), followed by removal of the template and Co (II) ions resulted in an esterase MIP (Figure 8). The incorporation of catalytic groups is responsible for the substrate specificity and catalytic activity within the imprinted cavities. The esterase MIP exhibited a 5- to 7-fold rate enhancement in the hydrolysis of Boc-Met (or Leu)-p-nitrophenyl ester over the control polymer esterase CP with statistically distributed imidazole groups. Nevertheless, the template molecule was not a TSA but an analogue of the substrate, which was likely the cause of the polymers rather low rate enhancement.
Preparation and in vitro/in vivo evaluation of a clonidine hydrochloride drug–resin suspension as a sustained-release formulation
Published in Drug Development and Industrial Pharmacy, 2021
Hongfei Liu, Xiaoya Xie, Chao Chen, Caleb Kesse Firempong, Yingshu Feng, Limin Zhao, Xuezhi Yin
Ion exchange resin is an insoluble ionic material which consists of a structural part (composed of the polymer matrix usually cross-linked by styrene and divinylbenzene) and a functional part (ionic active group). The resins can be categorized into cation and anion exchange resins because they contain groups with either positive or negative charges [8]. With its high ion exchange capacity, good absorption, physical and chemical stability, and insolubility in any solvent, as well as other excellent properties, it has become an ideal choice for taste masking and control drug release, especially for the slow and controlled release system in liquid form [9,10]. In the pharmaceutical industry, it is used to separate and purify biomolecules (proteins, nucleotides, and amino acids) while in tablet formulation, it can be used as a disintegrating agent due to its expansibility [11]. The ion exchange resin can also be used as the active component of drugs [12,13], such as cholestyramine for cholesterol reduction, sodium polystyrene sulfonate for potassium reduction, and sevelamer for treatment of hyperphosphatemia in patients with chronic renal failure. Few studies have been conducted on the application of ion exchange resins in antihypertensive drugs.
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