Afsal Manekkathodi

• Doctor of Philosophy
• Hamad bin Khalifa University

Bioenergetics is the study of how life-activities are powered within the cell. This also deals with the interactive exchange of matter/radiation between cellular components and their environment, and the accompanying changes thereof. The acclaimed bioenergetics paradigm has relied on “electron transport chains” and selective/stoichiometric electrog...

Bioenergetics is the study of how life-activities are powered within the cell. This also deals with the interactive exchange of matter/radiation between cellular components and their environment, and the accompanying changes thereof. The acclaimed bioenergetics paradigm has relied on ‘electron transport chains’ and selective/stoichiometric electrog...

The Z-scheme electron transport chain (ETC) explanation for photosynthesis starts with the serial/sequential transfer of electrons sourced from water molecules bound at Photosystem II via a deterministic array of redox centers (of various stationary/mobile proteins), before \"sinking\" via the reduction of NADP+ bound at flavin-enzyme reductase. Se...

Oxygenic photosynthesis essentially involves photo-lysis (splitting of water to release oxygen), photo-reduction (formation of NADPH), and photo-phosphorylation (synthesis of ATP) reactions. These reactions use photoactive pigments such as chlorophylls and carotenoids. Z-scheme and Kok-Joliot cycle, the acclaimed and deterministic model of photosyn...

Bicarbonate ion has been proposed as a potential source for electrons/O-atom in the light reaction of oxygenic photosynthesis, both in the pre-Zscheme era and in recent times. In the light of murburn concept being mooted as a viable explanation for photophosphorylation, we present substantial theoretical analysis which supports the proposal that: (...

In this first part of our essay on oxygenic photosynthesis, we address the various aspects of classical and murburn explanations. We had recently pointed out that the classical explanations of- trans-membrane potential (TMP)-based chemiosmotic rotary ATP synthesis, quinone-cycle at cytochrome b6f, chartered electron transport by plastocyanin, and m...

In this second half of our treatise on oxygenic photosynthesis, we provide support for the murburn model of the light reaction of photosynthesis and ratify key predictions made in the first part. Molecular docking and visualization of various ligands of quinones/quinols (and their derivatives) with PSII/Cytochrome b6f complexes did not support char...

The prevailing understanding on the light reaction of oxygenic photosynthesis (photolytic photophosphorylation & NADPH synthesis) considers the vast majority of the diverse pigments, chlorophyll binding proteins (CBPs) and light harvesting complexes (LHCs) as photon-energy relaying facets; only the chlorophyll a couplets at the reaction center of t...

The prevailing understanding on photolytic photophosphorylation, the light reaction of oxygenic photosynthesis, considers the vast majority of the diverse pigments, chlorophyll binding proteins (CBPs) and light harvesting complexes (LHCs) as photon-energy relaying facets; only the two photosystems’ (PS) reaction centers’ chlorophyll a couplets are...

We have recently questioned the long standing explicatory paradigm of Z-scheme of electron transfers leading to the reduction of NADP+, Kok-Joliot cycle of oxygenesis and chemiosmotic rotary ATP synthesis for the physiology of photolysis and photophosphoylation in chloroplasts. Here, we show that the diverse redox enzyme paradigms of xenobiotic met...

The severe instability and rapid degradation of hybrid organic-inorganic metal-halide perovskite materials under adverse environmental conditions is one of the major obstacles facing perovskite solar cell (PSC) technology in the path towards large-scale utilization. In this work, the first investigation of the degradation dynamics of the state-of-t...

Z-scheme is a spatio-temporally demarcated, sequential/serial and vitally deterministic purview of ‘electron transport chain’, purportedly explaining the light reaction of oxygenic photosynthesis. Herein, first, we summarize the salient components of Z-scheme: Kok-Joliot cycle, P680 cycle, Q-cycle, plastocyanin relay, P700 cycle, ferredoxin relay a...

Robert Emerson’s original observation (1957) that “oxygenesis occurs even with far-red light excitation of Photosystem I” is incompatible with the extant Kok-Joliot cycle’s foundation that “photolysis occurs only at red-light stimulated Photosystem II harboring MnComplex”. Further, the Z-scheme of electron transfer cannot account for Emerson’s obse...

A deep understanding of environmental effects on perovskite solar cell (PSC) performance is highly desirable for further progress towards large-scale deployment of this technology. We investigate the operation of PSCs in the temperature range (15−50 C) and report an unusual bimodal behavior in photovoltaic (PV) performance, with positive and negati...

We report stable perovskite solar cells having 3D/2D perovskite absorber layers and CuSCN as an inorganic hole transporting material (HTM). Phenylethylammonium (PEA) and 4-fluoro-phenylethylammonium (FPEA) have been chosen as 2D cations, creating thin layers of [PEA2PbI4] or [FPEA2PbI4] on top of the 3D perovskite. The 2D perovskite as an interfaci...

Multi-junction solar cells based on solution-processed metal halide perovskites offer a route to increased power conversion efficiency (PCE); however, the limited options for infrared (IR)-absorbing back cells have constrained progress. Colloidal quantum dot (CQD)-based solar cells, which are solution-processed and have bandgaps tunable to waveleng...

Since mid-1970s, the proton-centric proposal of 'chemiosmosis' became the acclaimed explanation for aerobic respiration. Recently, significant theoretical and experimental evidence were presented for an oxygen-centric 'murburn' mechanism of mitochondrial ATP-synthesis. Herein, we compare the predictive capabilities of the two models with respect to...

The long-standing explanation for cellular respiration (mitochondrial oxidative phosphorylation, mOxPhos) in textbooks is proton-centric and involves the elements of Rotary ATP synthesis, Chemiosmosis principle, Proton pumps and Electron transport chain (in short, the RCPE model). Addressing certain lacunae in the RCPE model, an alternative scheme...

CuI and CuSCN as Hole Transport Materials for Perovskite Solar Cells Vinod E. Madhavan1*, Ahmer Ali Bozdar Baloch1, Afsal Manekkathodi1, Dhanasekaran Thirunvukkaarasu1, I. Zimmermann2, C. Roldán- Carmona2, G. Grancini2, M. Buffiere1, Mohammad Khaja Nazeeruddin2, A. Belaidi1 and Nouar Tabet1 1 Qatar Environment and Energy Research Institute, Hamad B...