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β-Lactams and Related Compounds as Antibacterials and β-Lactamase Inhibitors
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
Ulrike Holzgrabe, Jens Schmitz
From the evolutionary point of view, penicillin-binding proteins (PBPs) and β-lactamases are related to each other with PBPs being the ancestors (Massova et al., 1998; Meroueh et al., 2003). They show substantial similarity in sequence and function. Both enzyme classes open the β-lactam ring by a nucleophilic attack of a serine-OH forming a covalent bound between substrate and enzyme (cf. Figs. 8.1b and 8.4). In addition, the serine-β-lactamases (SBLs) consist of a polar pocket, which attract the carboxylic acid of the β-lactams, and a sort of an oxyanion hole, which stabilizes the carbonyl oxygen of lactam rings. In β-lactamases, a basic amino acid, such as lysine or glutamine, activates the serine-OH by taking over the proton. The serine ester of the ring-opened β-lactam (acyl-enzyme species) will be attacked by water and the resulting deacylation of the lactamase will be fast in comparison to the deacylation of the PBP. Finally, the hydrolyzed β-lactam, a penicilloic acid, and the free enzyme are released and the enzyme is ready to attack the next antibiotic. Interestingly, the penicilloic acid derivatives are competitive inhibitors of the lactamases, but far less active (Ghebre-Sellassie et al., 1984; Badarau et al., 2005). However, due to the high doses of β-lactams administered in clinics this can be of relevance.
Fiber-Optic Sensors in Bioprocess Control
Published in John V. Twork, Alexander M. Yacynych, Sensors in Bioprocess Control, 2020
Fuh and coworkers [47] as well as Kulp et al. [48] have developed enzyme optrodes for the detection of penicillin. In a typical arrangement, a polymer membrane is covalently attached to the tip of a glass optical fiber. The membrane contains the enzyme penicillinase and a pH-sensitive fluorescent dye. The enzyme catalyzes the cleavage of the lactam ring of penicillin to produce penicilloic acid and, consequently, a pH change in the microenvironment. Response times are about 1 min, and linear response over the 0.25 to 10 mM penicillin G concentration range is observed. Of course, the response function depends on the pH of the sample solution and its buffer capacity.
Nanosensors for Food Contaminant Detection
Published in C. Anandharamakrishnan, S. Parthasarathi, Food Nanotechnology, 2019
Heera Jayan, L. Bhavani Devi, C. Anandharamakrishnan
Tetracycline (TC) is the most widely used veterinary drug for preventing intestinal infection and growth promotion, and excessive use may result in drug residuals. This residual TC could reach humans via the food chain and would cause harm to human health. TC was detected by using a fluorescence probe via the photoinduced electron transfer (PET) fluorescence quenching mechanism, which was constructed using a hybrid quantum dot/mesoporous silica/molecularly imprinted polymer (QD/MS/MIP). This molecular imprinting technology detects TC in the linear range of 50 to 1000 ng mL−1, with a limit of detection of 15 ng mL−1, and the corresponding recoveries were found to be 90.2–97.2% with relative standard deviations of 2.2–5.7% (Zhang and Chen et al., 2016). A simple enzymic penicillin biosensor with layer-by-layer (LbL) films of single-graphene nanosheets (SGN)-hematein/ILs/penicillinase was demonstrated for the detection of penicillin. The immobilized penicillinase catalyzes the hydrolysis of penicillin to penicilloic acid, where H+ is liberated and monitored amperometrically with hematein as a pH indicator. Therefore, the linear range of detection for penicillin using SGN-hematein/ILs/penicillinase biosensor was from 1.25 × 10−13 M to 7.5 × 10−3 M and a relatively low detection limit of 10−13 M (0.04 ppt). Moreover, the proposed method was applied for the detection of penicillin in milk, which exhibits acceptable reproducibility, stability, good specificity, and high sensitivity (Wu et al., 2014). Sulfamethazine (SMZ), one of the most frequently used sulfonamides (SA) in veterinary clinics, was detected using a chemiluminescence resonance energy transfer (CRET) technique by employing hapten functionalized quantum dots (QDs) in a competitive immunoassay. Amphiphilic polymers were used for the synthesis of core/multishell QDs, which was further functionalized using hapten 4-(4-aminophenyl sulfonamido)butanoic acid. The above described CRET based immunoassay detects SMZ with LOD of 9 pg mL–1, which was found to be greater than two orders of magnitude than a heterogeneous enzyme-linked immunosorbent assay and four orders of magnitude better than a homogeneous fluorescence polarization immunoassay (Ma et al., 2016).
Advanced Oxidation Technology (Ozone-catalyzed by Powder Activated Carbon - Portland Cement) for the Degradation of the Meropenem Antibiotic
Published in Ozone: Science & Engineering, 2021
Edison Alexander Agudelo, Santiago Alonso Cardona G.
The degradation of Meropenem occurs mainly through basic hydrolysis; as the above diagram shows, a concentration of Meropenem (6 mg/L) was eliminated during 24 hours of pH conditioning in cement paste. When analyzing the thermodynamics of the system, the reaction and ionization of the Meropenem is spontaneous (in its second pKa2), because the Meropenem spontaneously passes (negative Gibbs free energy) to the Meropenem salt form by means of basic hydrolysis through the rupture of the carbapenemic nucleus (nucleophilic substitution). When hydrolysis is carried out in a basic medium, the beta-lactam ring breaks as a first step due to its angular instability (angular tension), thus forming a type of acid analogous to penicilloic acid (meropenemoic), which reacts to form Meropenem salt. Hrabák et al. (2011) demonstrated through instrumental analysis (HPLC-MS), that when hydrolysis is carried out with sodium hydroxide (NaOH), a trisodium salt of Meropenem is produced.
Persulfate-based photodegradation of a beta-lactam antibiotic amoxicillin in various water matrices
Published in Environmental Technology, 2020
Eneliis Kattel, Balpreet Kaur, Marina Trapido, Niina Dulova
The formation of several transformation products of AMX was verified by LC-MS analysis. The measured mass (m/z) for protonated AMX was 366. In UW, the most frequently detected m/z in the UVC//Fe2+ and UVC/ systems were 122, 366, 382, that most likely correspond to penicilloic acid derivative (C7H8NO) [28], AMX-diketopiperazine-2′,5′ [29] and hydroxylated AMX, respectively. In GW, DW and STWW, the primary fragments were 208 and 366 of what the first could refer to AMX derivative C10H10NO2S [28]. Primary proposed pathways of the transformation products are shown in Figure 5. Hydroxylation of AMX resulted in m/z of 382 (Figure 5 route A), opening of the unstable beta-lactam ring by hydrolysis yields in the intermediate product AMX-penicilloic acid which rapidly forms more stable AMX-diketopiperazine-2′,5′ (Figure 5 route B). Another possible final product of the AMX degradation could be C7H8NO that forms after opening of the beta-lactam ring followed by demethylation, decarboxylation, opening of the thiazole ring and loss of S atom (Figure 5 route C). Decarboxylation, demethylation and opening of the thiazole ring may result in the formation of AMX derivative C10H10NO2S (Figure 5 route D).