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Styrene maleic acid (SMA) polymers have proven to be very successful for the extraction of membrane proteins, forming SMA lipid particles (SMALPs), which maintain a lipid bilayer around the membrane protein. SMALP-encapsulated membrane proteins can be used for functional and structural studies. The SMALP approach allows retention of important protein-annular lipid interactions, exerts lateral pressure, and offers greater stability than traditional detergent solubilisation. However, SMA polymer does have some limitations, including a sensitivity to divalent cations and low pH, an absorbance spectrum that overlaps with many proteins, and possible restrictions on protein conformational change. Various modified polymers have been developed to try to overcome these challenges, but no clear solution has been found. A series of partially-esterified variants of SMA (SMA 2625, SMA 1440 and SMA 17352) has previously been shown to be highly effective for solubilisation of plant and cyanobacterial thylakoid membranes. It was hypothesised that the partial esterification of maleic acid groups would increase tolerance to divalent cations. Therefore, these partially-esterified polymers were tested for the solubilisation of lipids and membrane proteins, and their tolerance to magnesium ions. It was found that all partially esterified polymers were capable of solubilising and purifying a range of membrane proteins, but the yield of protein was lower with SMA 1440, and the degree of purity was lower for both SMA 1440 and SMA 17352. SMA 2625 performed comparably to SMA 2000. SMA 1440 also showed an increased sensitivity to divalent cations. Thus, it appears the interactions between SMA and divalent cations are more complex than proposed and require further investigation., Graphical abstract Unlabelled Image, Highlights • Partially-esterified SMA polymers are effective for solubilisation of membrane proteins from different expression systems. • Proteins in partially-esterified SMALPs can be purified by Ni2+ affinity chromatography, but yield is lower with SMA 1440. • Partial esterification of SMA does not overcome the sensitivity to divalent cations. • SMA1440 is more sensitive to magnesium ions than SMA 2000.

Urease enzyme (UE) has been reported to be a potent virulence factor for Helicobacter pylori (HP) bacteria indicated to be responsible for various gastrointestinal diseases. Therefore, the spread of HP, currently regarded by the World Health Organization as a class 1 carcinogen, could be better controlled by targeting UE. It is in this line that we have synthesized three new derivatives (2–4) of the naturally occurring olean-12-en-3-one (1), which was previously isolated from the figs of Ficus vallis-choudae Delile (Moraceae). Among the synthesized compounds, 3 and 4 contain an indole moiety. Their structures were unambiguously assigned by spectroscopic and spectrometric techniques (1D-NMR, 2D-NMR and MS). The starting material and the synthesized compounds were screened for UE inhibition activity, and showed significant activities with IC50 values ranging from 14.5 to 24.6 μM, with compound (1) being the most potent as compared to the positive control thiourea (IC50 = 21.6 μM). Amongst the synthetic derivatives, compound 4 was the most potent (IC50 = 17.9 μM), while the others showed activities close to that of the control. In addition, molecular docking study of target compounds 2–4 was performed in an attempt to explore their binding mode for the design of more potent UE inhibitors. Graphical Abstract Electronic supplementary material The online version of this article (10.1007/s13659-018-0193-7) contains supplementary material, which is available to authorized users.

Since the demand for self-sustained wireless systems is increasing, there is a trend towards RF energy harvesting. It is a key solution to energize the low power systems such as the Internet of Things (IoT) devices without replacing the batteries periodically. This paper presents the design and analysis of RF energy harvesting system that consists of dual-band microstrip patch antenna operating at 2.4 GHz and 5.8 GHz, an impedance matching network, 4-stage voltage doubler and a storing circuit. The antenna is designed using ADS Agilent and sonnet suites software that provides a directivity of 5.5 dBi and 6.3 dBi at 2.4 GHz and 5.8 GHz respectively. The measured results of the fabricated antenna are well agreement with the simulated results. Simulated results show that for an input received power of 10 mW, the proposed system can provide 4.5 mW power at the output of 4-stage voltage rectifier with an overall efficiency of 45%.