Honey is becoming accepted as a reputable and effective therapeutic agent by practitioners of conventional medicine and by the general public. It has many biological activities and has been effectively used in the treatment of many diseases, e.g. gastrointestinal diseases, skin diseases, cancer, heart diseases, and neurological degeneration. Honey is an excellent source of energy containing mainly carbohydrates and water, as well as, small amounts of organic acids, vitamins, minerals, flavonoids, and enzymes. As a natural product with a relatively high price, honey has been for a long time a target for adulteration. The authenticity of honey is of great importance from commercial and health aspects. The study of the physical and chemical properties of honey has been increasingly applied as a certification process for the purpose of qualification of honey samples. The current work focusses on studying the authenticity of various types of honey sold in Riyadh market (24 samples). For this purpose, physical properties (pH, hydroxylmethylfurfural HMF, and pollen test) were measured. Besides, sugar composition was evaluated using Fehling test and an HPLC method. Elemental analysis was carried out using inductively coupled plasma (ICP). In addition, the presence of drug additives was assessed by means of GC–MS. The obtained results were compared with the Saudi Arabian standards, Codex Alimentarius Commission (2001), and harmonized methods of the international honey commission.

Small-conductance Ca2+-activated K+ (SK) channels mediate medium afterhyperpolarization in the neurons and play a key role in the regulation of neuronal excitability. SK channels are potential drug targets for ataxia and Amyotrophic Lateral Sclerosis (ALS). SK channels are activated exclusively by the Ca2+-bound calmodulin. Previously, we identified an intrinsically disordered fragment that is essential for the mechanical coupling between Ca2+/calmodulin binding and channel opening. Here, we report that substitution of a valine to phenylalanine (V407F) in the intrinsically disordered fragment caused a ~6 fold increase in the Ca2+ sensitivity of SK2-a channels. This substitution resulted in a novel interaction between the ectopic phenylalanine and M411, which stabilized PIP2-interacting residue K405, and subsequently enhanced Ca2+ sensitivity. Also, equivalent valine to phenylalanine substitutions in SK1 or SK3 channels conferred Ca2+ hypersensitivity. An equivalent phenylalanine substitution in the Caenorhabditis elegans (C. elegans) SK2 ortholog kcnl-2 partially rescued locomotion defects in an existing C. elegans ALS model, in which human SOD1G85R is expressed at high levels in neurons, confirming that this phenylalanine substitution impacts channel function in vivo. This work for the first time provides a critical reagent for future studies: an SK channel that is hypersensitive to Ca2+ with increased activity in vivo.

Small-conductance Ca2+-activated K+ (SK) channels play essential roles in the regulation of cellular excitability and have been implicated in neurological and cardiovascular diseases through both animal model studies and human genetic association studies. Over the past two decades, positive modulators of SK channels such as NS309 and 1-EBIO have been developed. Our previous structural studies have identified the binding pocket of 1-EBIO and NS309 that is located at the interface between the channel and calmodulin. In this study, we took advantage of four compounds with potencies varying over three orders of magnitude, including 1-EBIO, NS309, SKS-11 (6-bromo-5-methyl-1H-indole-2,3-dione-3-oxime) and SKS-14 (7-fluoro-3-(hydroxyimino)indolin-2-one). A combination of x-ray crystallographic, computational and electrophysiological approaches was utilized to investigate the interactions between the positive modulators and their binding pocket. A strong trend exists between the interaction energy of the compounds within their binding site calculated from the crystal structures, and the potency of these compounds in potentiating the SK2 channel current determined by electrophysiological recordings. Our results further reveal that the difference in potency of the positive modulators in potentiating SK2 channel activity may be attributed primarily to specific electrostatic interactions between the modulators and their binding pocket.

Background and Purpose: In the activated state of small-conductance Ca 2+ -activated potassium (K Ca 2) channels, calmodulin interacts with the HA/HB helices and the S4-S5 linker. CyPPA potentiates K Ca 2.2a and K Ca 2.3 channel activity but not the K Ca 2.1 and K Ca 3.1 subtypes.Experimental Approach: Site-directed mutagenesis, patch-clamp recordings and in silico modelling were utilised to explore the structural determinants for the subtypeselective modulation of K Ca 2 channels by CyPPA.

Aim Small‐conductance Ca2+‐activated potassium (SK) channels are activated exclusively by increases in intracellular Ca2+ that binds to calmodulin constitutively associated with the channel. Wild‐type SK2 channels are activated by Ca2+ with an EC50 value of ~0.3 μmol/L. Here, we investigate hydrophobic interactions between the HA helix and the S4‐S5 linker as a major determinant of channel apparent Ca2+ sensitivity. Methods Site‐directed mutagenesis, electrophysiological recordings and molecular dynamic (MD) simulations were utilized. Results Mutations that decrease hydrophobicity at the HA‐S4‐S5 interface lead to Ca2+ hyposensitivity of SK2 channels. Mutations that increase hydrophobicity result in hypersensitivity to Ca2+. The Ca2+ hypersensitivity of the V407F mutant relies on the interaction of the cognate phenylalanine with the S4‐S5 linker in the SK2 channel. Replacing the S4‐S5 linker of the SK2 channel with the S4‐S5 linker of the SK4 channel results in loss of the hypersensitivity caused by V407F. This difference between the S4‐S5 linkers of SK2 and SK4 channels can be partially attributed to I295 equivalent to a valine in the SK4 channel. A N293A mutation in the S4‐S5 linker also increases hydrophobicity at the HA‐S4‐S5 interface and elevates the channel apparent Ca2+ sensitivity. The double N293A/V407F mutations generate a highly Ca2+ sensitive channel, with an EC50 of 0.02 μmol/L. The MD simulations of this double‐mutant channel revealed a larger channel cytoplasmic gate. Conclusion The electrophysiological data and MD simulations collectively suggest a crucial role of the interactions between the HA helix and S4‐S5 linker in the apparent Ca2+ sensitivity of SK2 channels.