Ultrafast energy transfer between lipid-linked chromophores and plant light-harvesting complex II

Light-Harvesting Complex II (LHCII) is a membrane protein found in plant chloroplasts that has the crucial role of absorbing solar energy and subsequently performing excitation energy transfer to the reaction centre subunits of Photosystem II. LHCII provides strong absorption of blue and red light, however, it has minimal absorption in the green spectral region where solar irradiance is maximal. In a recent proof-of-principle study, we enhanced the absorption in this spectral range by developing a biohybrid system where LHCII proteins together with lipid-linked Texas Red (TR) chromophores were assembled into lipid membrane vesicles. The utility of these systems was limited by significant LHCII quenching due to protein–protein interactions and heterogeneous lipid structures. Here, we organise TR and LHCII into a lipid nanodisc, which provides a homogeneous, well-controlled platform to study the interactions between TR molecules and single LHCII complexes. Fluorescence spectroscopy determined that TR-to-LHCII energy transfer has an efficiency of at least 60%, resulting in a 262% enhancement of LHCII fluorescence in the 525–625 nm range, two-fold greater than in the previous system. Ultrafast transient absorption spectroscopy revealed two time constants of 3.7 and 128 ps for TR-to-LHCII energy transfer. Structural modelling and theoretical calculations indicate that these timescales correspond to TR–lipids that are loosely- or tightly-associated with the protein, respectively, with estimated TR-to-LHCII separations of ∼3.5 nm and ∼1 nm. Overall, we demonstrate that a nanodisc-based biohybrid system provides an idealised platform to explore the photophysical interactions between extrinsic chromophores and membrane proteins with potential applications in understanding more complex natural or artificial photosynthetic systems

Chitosan fiber-supported zero-valent iron nanoparticles as a novel sorbent for sequestration of inorganic arsenic

This study proposes a new sorbent for the removal of inorganic arsenic from aqueous solutions. Monodispersed nano zero-valent iron (nZVI) particles were nucleated at the surface of electrospun chitosan fibers (average fiber diameter of 195 ± 50 nm) by liquid phase reduction of FeCl3 using NaBH4. The material was characterized using SEM, TGA, XPS, XRD, and FTIR. The diameter of iron nanoparticles was found to vary between 75-100 nm. A set of batch experiments were carried out to elucidate the efficiency of the composite sorbent toward fixation of arsenite and arsenate ions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed that the chitosan fiber supported nZVI particles is an excellent sorbent material for inorganic arsenic uptake at concentrations ranging from 0.01 to 5.00 mg L -1 over a wide range of pH values. Based on XPS analysis, As(iii) was found to undergo oxidation to As(v) upon sorption, while As(v) retained its oxidation state. By virtue of the successful combination of the electrospun fibers' mechanical integrity and the large reactivity of dispersed nZVI particles, the applicability of the resulting sorbent material in arsenic sorption holds broad promise

Green synthesis of iron nanoparticles and their application as a Fenton-like catalyst for the degradation of aqueous cationic and anionic dyes

Iron nanoparticles were produced using extracts of green tea leaves (GT-Fe NPs). The materials were characterized using TEM, SEM/EDX, XPS, XRD, and FTIR techniques and were shown to contain mainly iron oxide and iron oxohydroxide. The obtained nanoparticles were then utilized as a Fenton-like catalyst for decolorization of aqueous solutions containing methylene blue (MB) and methyl orange (MO) dyes. The related experiments investigated the removal kinetics and the effect of concentration for both MB and MO. The concentrations of dyes in aqueous solution were monitored using ultraviolet–visible (UV–vis) spectroscopy. The results indicated fast removal of the dyes with the kinetic data of MB following a second order removal rate, while those of MO were closer to a first order removal rate. The loading experiments indicated almost complete removal of both dyes from water over a wide range of concentration, 10–200 mg L−1. Compared with iron nanoparticles produced by borohydride reduction, GT-Fe nanoparticles demonstrated more effective capability as a Fenton-like catalyst, both in terms of kinetics and percentage removal.Birzeit Universit

Ultrafast energy transfer between lipid-linked chromophores and plant light-harvesting complex II

We characterize the photophysical interactions between lipid-linked chromophores and plant light-harvesting proteins incorporated into nanodiscs using optical spectroscopy, simulations and theoretical modelling.</jats:p

Ultrafast Energy Transfer Between Lipid-Linked Chromophores and Plant Light-Harvesting Complex II

Light-Harvesting Complex II (LHCII) is a membrane protein found in plant chloroplasts that has the crucial role of absorbing solar energy and subsequently performing excitation energy transfer to the reaction centre subunits of Photosystem II. LHCII provides strong absorption of blue and red light, however, it has minimal absorption in the green spectral region where solar irradiance is maximal. In a recent proof-of-principle study, we enhanced the absorption in this spectral range by developing a biohybrid system where LHCII proteins together with lipid-linked Texas Red (TR) chromophores were assembled into lipid membrane vesicles. The utility of these systems was limited by significant LHCII quenching due to protein-protein interactions and heterogeneous lipid structures. Here, we organise TR and LHCII into a lipid nanodisc, which provides a homogeneous, well-controlled platform to study the interactions between TR molecules and single LHCII complexes. Fluorescence spectroscopy determined that TR-to-LHCII energy transfer has an efficiency of at least 60%, resulting in a 255% enhancement of LHCII fluorescence, two-fold greater than in the previous system. Ultrafast transient absorption spectroscopy revealed two time constants of 3.7 and 128 ps for TR-to-LHCII energy transfer. Structural modelling and theoretical calculations indicate that these timescales correspond to TR-lipids that are loosely- or tightly-associated with the protein, respectively, with estimated TR-to-LHCII separations of ~3.5 nm and ~1 nm. Overall, we demonstrate that a nanodisc-based biohybrid system provides an idealised platform to explore the photophysical interactions between extrinsic chromophores and membrane proteins with potential applications in understanding more complex natural or artificial photosynthetic systems

Assessment of practices and awareness regarding the disposal of unwanted pharmaceutical products among community pharmacies: a cross-sectional study in Palestine

Abstract Background The improper disposal of pharmaceutical preparations substantially threatens human health and environmental safety. Pharmacists are responsible for properly disposing of unwanted medications and educating patients about how to do so themselves. This study aimed to assess community pharmacists’ knowledge, determine their views on how to dispose of unwanted pharmaceuticals, and assess the extent to which they realize that it is their responsibility to guide patients toward the safe disposal of expired medications. Methods A descriptive cross-sectional study was conducted between December 2021 and April 2022 among 400 practicing pharmacists who were chosen to participate by random cluster sampling. Community pharmacists’ practices, awareness, and beliefs about disposing of unused drugs were evaluated. The Statistical Package for Social Sciences (IBM-SPSS) version 21 was used for data entry and analysis. Results Of 400 pharmacists, 348 stated that they did not participate in courses on the safe disposal of unwanted medications. Disposal of drugs in the garbage, an unsafe method, was very frequently recommended by pharmacists to patients, especially regarding inhalers, antibiotics, hormonal drugs, and solid and semisolid drugs. However, many pharmacists advised patients to return their hormonal, category B, and category C drugs to the pharmacy. A total of 61.3% of pharmacists agreed and 26% strongly agreed that unsafe disposal of drugs negatively affects the environment. A total of 54.3% of the participants agreed that improper disposal of antibiotics might be a reason for increased antimicrobial resistance, and 54.5% of them agreed that improper disposal of hormonal drugs might contribute to the development of certain cancers. A total of 80.3% of the participants perceived that most unwanted drugs in pharmacies were those returned from patients. A total of 97.3% of the participants supported establishing a drug disposal system, with 77.5% choosing to have the district health board responsible for funding this system. A total of 48.5% of the participants indicated that a lack of education and awareness on the issue of getting rid of unused drugs constitutes a challenge to the safe disposal of medicines, and 66% of them said that a lack of law enforcement constitutes another challenge. A total of 95.5% of the participants agreed or strongly agreed that good training for health sector workers and organizing workshops to develop knowledge on this subject would improve practices. A total of 93.3% supported distributing educational brochures, and 92.8% supported placing special containers in every pharmacy to collect unwanted drugs. Conclusions Most pharmacists in our study returned drugs to manufacturing companies and stores, and few followed the correct methods of incineration and return of drugs to the Ministry of Health. Current data emphasize the issue of improper disposal of medicine in Palestine and the need for improved education among healthcare workers