Wyniki wyszukiwania - BazTech

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Zastosowanie detektora wyładowań koronowych (CAD) w analizach chemicznych

Kijewska I., Frączak O., Wilczek R.

Laboratorium - Przegląd Ogólnopolski

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2018

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nr 2

20--25

PL

W ostatnich latach obserwujemy wzrost wykorzystania detektora wyładowań koronowych (CAD) sprzężonego z chromatografem cieczowym w analizach produktów spożywczych, farmaceutycznych, kosmetycznych i innych. Technika ta charakteryzuje się wysoką czułością i szerokim zakresem dynamicznym, a odpowiedź substancji badanej jest niezależna od jej struktury chemicznej. W pracy opisano zasadę działania CAD oraz przedstawiono wybrane zastosowania w analizach związków niezawierających chromoforów i w analizach mających na celu zredukowanie liczby wzorców.

EN

In recent years we have seen an increase in the use of a corona charged aerosol detector (CAD) coupled with liquid chromatography in the analyses of food, pharmaceuticals, cosmetics and others. This technique is characterized by high sensitivity and a wide dynamic range, while the analyte response does not depend on its chemical structure. In the paper we explain the operating principle of CAD and provide its exemplary applications in the analyses of compounds without chromophores and the analyses aimed at reducing the number of used standards.

2

Metoda O-acyloizopeptydowa w syntezie peptydow

Frączak O., Olma A.

Wiadomości Chemiczne

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2014

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[Z] 68, 7-8

733--749

EN

Proteins are macromolecules that carry out most of the biochemical functions of the cell, which strongly depend on the secondary and tertiary structure, defined by the amino acid sequence of a polypeptide chain. The importance of peptides and proteins in biology and medicine inspired chemists to develop strategies for their synthesis. The main limitation to the preparation of long peptides is their tendency to aggregation, what makes the coupling and deprotection reaction ineffective, and purification of the compounds difficult. Inter- and intramolecular interactions, hydrophobic character, the presence of multiple hydrogen bonds significantly affect the secondary structure of peptides, making further extension of the peptide chain very difficult. Undesirable aggregation process may be disrupted by reduction of hydrophobic interactions. For this purpose, various methods are used, based on the implementation of specific modifications to the peptide chain, affecting its secondary structure. These methods include, for example, incorporation of pseudoproline building blocks [5] and proximity induced peptide ligation [6, 7]. In some cases, it is convenient to extend the amino acid side chain to form isopeptides (Fig. 1) [14–16]. Depsipeptides can be created with the natural amino acids such as cysteine, serine, threonine, tyrosine, or tryptophan. The basic requirement is the presence of β-hydroxyamino component. The presence of a depsipeptide moiety in place of an amide bond significantly change the secondary structure of native peptide and prevents from aggregation, leading to higher yields of desired compounds [18]. In the solution phase peptide synthesis, this method is free from racemization [19]. Isodipeptide units can be successfully applied in SPPS for the synthesis of “difficult sequence”-containing peptides [19]. In this paper, many examples of effective use of O-acylisopeptides method in peptide synthesis are discussed.

3

Biwalentne ligandy receptorów opioidowych

Frączak O., Olma A.

Wiadomości Chemiczne

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2014

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[Z] 68, 3-4

233--255

EN

Opioids are the oldest drugs know to humanity, which have been and continue to be used for the treatment of chronic pain. Unfortunately they have a large numbers of side effects [1–6]. Three main types of opioid receptors μ (MOR), δ (DOR) and κ (KOR) are known [8]. The ORL1 receptor was classified as the fourth member of opioid receptor family [9]. Opioid receptors can form homodimers and the following heterodimers: DOR-KOR, DOR-MOR and KOR-MOR [13c,d,f, 14]. Specially designed ligands which are able to penetrate the BBB are used to study physiological consequences of opioid receptor homo- and heterodimerization, and as new analgesics. Bivalent ligands are defined as compounds that contain two pharmacophoric units, an appropriately designed spacer to separate and define the two pharmacophores, and a linker unit to connect the pharmacophores, to the spacer (Fig. 1) [16]. The affinity of a ligand to its target depends on its fundamental kinetic association and dissociation rate constants (Scheme 1) [24]. Bivalent ligands interacting with the opioid receptors have been divided into three groups: nonpeptide, peptide- nonpeptide and peptide homo- or heterodimers. Nonpeptide bivalent ligands (4–21, 27–41 and 44–45) containing different pharmacophores (selective opioid agonists or/and antagonists) connected with designed linkers have potent analgesic properties [25–34]. Compound 35 may be useful in the treatment of opioid dependence. Studies of peptide-nonpeptide ligands, which are a combination of “address” segments of endogenous opioid peptides and selective alkaloid ligand (47–50) indicate that peptide part of the analogues can modulate the receptor selectivity of the attached alkaloid pharmacophores [35]. Series of peptide-nonpeptide ligands containing different classes of opioid peptides and fentanyl (52–86) were synthesized and tested for binding affinity to μ and δ opioid receptors [38–40]. Good opioid affinity and antinociceptive activity of some of the obtained bivalent ligands (57, 61, 63) suggesting that a novel class of analgesics can be further developed utilizing this approach. Among homobivalent ligands the most important is biphalin 87 and its analogues (88–124) [41–53]. Analgesic potency of the most active ligand 112 is greater than parent peptide (biphalin) and morphine.