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10 Whereas, for the attachment to a protein, or another source of amine functional groups, N-hydroxysuccinimide (NHS) esters are common. 9 For the direct attachment to gold surfaces disulfides, such as the lipoic acid tether of compound 5, are ubiquitous. 8 Another commonly used bio-compatible reaction is the copper-catalysed click reaction in which an alkyne, such as in compound 4, reacts with an azide to form a triazole. Compounds 2–6 were designed to include commonly employed functional groups that are used in biocompatible reactions with surfaces and other substrates of interest.Ĭompounds 2 and 3 both feature a maleimide this motif is a prevalent functional handle used for selective reaction through conjugation with thiol groups.
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In addition to the previously reported compounds 2 and 3, 7 a further seven analogues were synthesised, Fig. The amine motif provided a functional handle for the addition of the desired chemical tether through amidation reactions, allowing access to a selection of compounds with reactive pendant groups. This position was chosen to minimise the effect of the tether on the pharmacophore, the β-lactam ring. The modifications to 1 described herein were performed via the amine of the molecule. Here, we set out to investigate the effect of the addition of a chemical tether on the properties of the parent compound, thus contributing new SAR information.Ĭompound design. Studies of the surface-bound antibiotic demonstrated that β-lactamases and a penicillin binding protein (PBP) were able to recognise and bind the immobilised drugs. 7 In order to attach the antibiotic molecule to the surface, an analogue of cephalexin ( 1) was prepared featuring a maleimide group attached via a PEG linker ( 2), Fig. Recently, we demonstrated the ability of surface bound β-lactam drugs to be recognised by the therapeutic target proteins as well as enzymes produced by resistant bacteria. 4 Since their discovery, there has been extensive research carried out into the derivatisation of the β-lactam scaffold, resulting in the successful development of numerous antibiotics. The β-lactam antibiotics are widely used and are typically considered to be one of the safest classes of antibiotics.
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With the difficulties faced in the development of novel antibiotics and the increasing challenges of fighting against antibiotic resistance, 2,3 investigations into the SAR of antibiotic analogues could reveal valuable information. Consequently, opportunities to gain insights into the structure–activity relationships (SAR) are missed. 1 However, the effect of such modifications on the function of a probe are often not evaluated, even though binding interactions are likely to be affected. A common approach is to attach a linker to the probe, such as a bifunctional polyethylene glycol (PEG), with orthogonal functional groups that allows for controlled reaction with the probe and with the desired substrate. The immobilisation or bioconjugation of a molecular probe often requires structural modification to introduce a functional handle, able to react with a desired substrate. This a key step in the preparation of many (bio)sensors, for example, which are designed for selective and sensitive detection of analytes. Introduction The controlled functionalisation of surfaces is imperative for the preparation of functional materials. Furthermore, the antimicrobial activity of the derivatives was evaluated to investigate the effect of the structural modifications on the antimicrobial activity of the parent drug, cephalexin.
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CTX-M-15 was found to favour hydrolysis of the parent antibiotic without a tether, whereas AmpC and NDM-1 were found to favour the modified analogues. In addition, the deactivation of the modified drugs by four β-lactamases (TEM-1, CTX-M-15, AmpC, NDM-1) was investigated and the effect of the tethers on the catalytic efficiencies determined. Herein, the activity of the modified antibiotics was evaluated for binding to the therapeutic target, the penicillin binding proteins, and shown to maintain binding interactions. The tethers were positioned remotely from the β-lactam ring to ensure minimal effect to the antibiotic's pharmacophore.
#Pbp3 ecoli uniprot series#
A series of cephalexin derivatives was prepared, equipped with chemical tethers suitable for the site-selective conjugation of antibiotics to functionalised surfaces. Here, we set out to determine the effects of attaching functional handles to a first-generation cephalosporin. Molecular probes typically require structural modifications to allow for the immobilisation or bioconjugation with a desired substrate but the effects of these changes are often not evaluated.