Search

Enzymes and membrane protein receptors represent almost three-quarters of all current drug targets. As a result, it would be beneficial to have a platform to produce them in a high-throughput format for drug screening. We have developed a miniaturized fluid array device for cell-free protein synthesis, and the device was exploited to produce both soluble and membrane proteins. Two membrane-associated proteins, bacteriorhodopsin and ApoA lipoprotein, were coexpressed in an expression medium in the presence of lipids. Simultaneous expression of ApoA lipoprotein enhanced the solubility of bacteriorhodopsin and would facilitate functional studies. In addition, the device was employed to produce two enzymes, luciferase and [beta]-lactamase, both of which were demonstrated to be compatible with enzyme inhibition assays. [beta]-lactamase, a drug target associated with antibiotic resistance, was further used to show the capability of the device for drug screening. [beta]-Lactamase was synthesized in the 96 units of the device and then assayed by a range of concentrations of four mock drug compounds without harvesting and purification. The inhibitory effects of these compounds on [beta]-lactamase were measured in a parallel format, and the degree in their drug effectiveness agreed well with the data in the literature. This work demonstrated the feasibility of the use of the fluid array device and cell-free protein expression for drug screening, with advantages in less reagent consumption, shorter analysis time, and higher throughput. 10.1021/ac1015479

This paper presents a ricin detection method based on ricin's inhibitory effects on protein synthesis. Biological synthesis (expression) of a protein includes the steps of gene transcription (DNA [right arrow] RNA) and protein translation (RNA [right arrow] proteins); these reactions can be coupled into a one-step operation and carded out in a cell-free medium. Ricin is known to inhibit protein synthesis by interacting with 28S ribosome RNA; the inhibitory effect is exploited as the sensing mechanism in this work. For each copy of DNA, thousands of copies of proteins can be produced. As a result, the inhibitory effects of ricin are amplified, leading to a significantly enhanced detection signal (the difference between the positive control and samples). An array of protein expression units is developed to accommodate positive/negative controls and multiple samples. The array device contains a solution without any reagent captured on a solid surface, offering flexibility without comprising the activities of biomolecules. The miniaturized well-in-a-well design possesses a mechanism to supply nutrients continuously and remove byproducts, leading to higher protein expression yields and thus larger detection signals (lower detection limit) when ricin is present. We demonstrate the production of green fluorescent protein and luciferase in the device. A calibration curve has been obtained between the luciferase expression yield and the ricin concentration, showing a detection limit of 0.01 nM (0.3 ng/mL) ricin. The nested-well device is also used for measuring the toxicity level of ricin after physical or chemical treatment.

A novel concept for toxin detection is presented that is based on the inhibitory effects of certain toxins on protein synthesis. Biological synthesis of proteins is called protein expression, which consists of the steps of DNA transcription and protein translation. In the toxin detection concept, a group of proteins are expressed simultaneously in a device consisting of an array of miniaturized wells. The expression yields of these proteins are inhibited by presence of a toxin. Differential inhibitory effects of each toxin on the expression of proteins in wells result in a response pattern (or signature) of the array device, which can be used as a tool for detection and identification of known and unknown agents. The concept has been demonstrated by in vitro protein expression of three proteins, including green fluorescent protein (GFP), chloramphenicol acetyltransferase (CAT), and luciferase. The production yields of these proteins in a cell-free medium were inhibited differentially by two toxin simulants, tetracycline (TC) and cycloheximide (CH). We confirmed that TC has an inhibitory effect on the production of GFP and CAT in the E. coli expression system whereas CH has a negligible effect. Moreover, the degree of TC's inhibitory effect on GFP is different from that on CAT. We also observed an opposite disparity; TC has a negligible inhibitory effect on the luciferase production in the rabbit reticulocyte expression system, whereas CH has a significant inhibitory effect. In addition, we obtained a response pattern in a 3 x 4 array device; the results suggest the feasibility of toxin detection based on the mechanisms of toxin actions. The device and method are also likely applicable to high-throughput drug screening, evident from the fact that TC is an antibiotic medicine.

Bacterial biofilms are surface-attached communities comprised of nonreplicating persister cells housed within a protective extracellular matrix. Biofilms display tolerance toward conventional antibiotics, occur in ∼80% of infections, and lead to >500000 deaths annually. We recently identified halogenated phenazine (HP) analogues which demonstrate biofilm-eradicating activities against priority pathogens; however, the synthesis of phenazines presents limitations. Herein, we report a refined HP synthesis which expedited the identification of improved biofilm-eradicating agents. 1-Methoxyphenazine scaffolds were generated through a Buchwald-Hartwig cross-coupling (70% average yield) and subsequent reductive cyclization (68% average yield), expediting the discovery of potent biofilm-eradicating HPs (e.g., 61: MRSA BAA-1707 MBEC = 4.69 μM). We also developed bacterial-selective prodrugs (reductively activated quinone-alkyloxycarbonyloxymethyl moiety) to afford HP 87, which demonstrated excellent antibacterial and biofilm eradication activities against MRSA BAA-1707 (MIC = 0.15 μM, MBEC = 12.5 μM). Furthermore, active HPs herein exhibit negligible cytotoxic or hemolytic effects, highlighting their potential to target biofilms.

Persistent bacteria, including persister cells within surface-attached biofilms and slow-growing pathogens lead to chronic infections that are tolerant to antibiotics. Here, we describe the structure-activity relationships of a series of halogenated phenazines (HP) inspired by 2-bromo-1-hydroxyphenazine 1. Using multiple synthetic pathways, we probed diverse substitutions of the HP scaffold in the 2-, 4-, 7-, and 8-positions, providing critical information regarding their antibacterial and bacterial eradication profiles. Halogenated phenazine 14 proved to be the most potent biofilm-eradicating agent (≥99.9% persister cell killing) against MRSA (MBEC < 10 μM), MRSE (MBEC = 2.35 μM), and VRE (MBEC = 0.20 μM) biofilms while 11 and 12 demonstrated excellent antibacterial activity against M. tuberculosis (MIC = 3.13 μM). Unlike antimicrobial peptide mimics that eradicate biofilms through the general lysing of membranes, HPs do not lyse red blood cells. HPs are promising agents that effectively target persistent bacteria while demonstrating negligible toxicity against mammalian cells.