PMC

Exacerbation of water scarcity resulting from additional water required for hydrogen production in 2050 through water electrolysis, compared to current water withdrawals for agricultural, industrial, and municipal activities. Power production from a solar panels and b onshore wind. The demand for water in hydrogen production alone does not create water scarcity in countries where it is not already present. However, the additional water demand for hydrogen production can exacerbate scarcity in countries already affected by water scarcity. Countries without color in the figure do not experience water scarcity. Gray-colored countries indicate unavailable data. The maps are created with the Matplotlib and Geopandas packages for Python^,.

Movements and interactions of TrpVI:13 and a bulk water molecule (“new water”) being transported into the water hydrogen bonding network during MD simulation. a, χ₁ of TrpVI:13 (in black) and z-coordinate of new water (NW) molecule (in purple) over the course of the simulation with TrpVI:13 in a starting position manually rotated into its presumed active conformation. b, hydrogen bonds observed between new water and polar residues in the receptor during the simulation. Each time a hydrogen bond was present this was marked with a “+.” A hydrogen bond was defined as described under “Experimental Procedures.” The hydrogen bonds colored blue represent hydrogen bonds to residues in the binding pocket, the purple hydrogen bonds are hydrogen bond to TrpVI:13, and the green hydrogen bonds are to polar residues in the hydrogen bonding network. c, snapshots of the hydrogen bonds between new water and selected residues in the receptor at key points in time as indicated by vertical arrows and dotted lines in a and b: 0.75 ns, hydrogen bond to TrpVI:13 still in the trans conformation; 0.80 ns, new water following TrpVI:13 as it rotates back to its inactive conformation; 0.95 ns, TrpVI:13 closing off the water hydrogen bond network and new water making hydrogen bonds to polar residues of the network.

Water-mediated hydrogen at the protein-DNA interface near position 72. (A) (a) Crystal structure of the Sox18-DNA complex with associated waters (pale cyan spheres) represented in a water box with spheres of hydration. (b) the positions occupied by three water molecules during MD simulation of 200 ns for Sox18-WT to illustrate motion of bulk water (green and pale cyan). Motion of one of the bulk waters (pale cyan) traced with connecting broken lines. The bridging water between hydroxyl group of Tyr72 and phosphate of DNA tracked in blue color during single water-mediated hydrogen bond between Ile5-Tyr72-DNA. (c) Transition of one water to two water-mediated hydrogen bond involving the backbone carbonyl of Ile5-Tyr72-DNA for Sox18-DNA complex. The bridging single water (blue) in exchange with bulk water (indicated by the connected lines of its trajectory after leaving its bridging position). Over the course of time, another water (green) is accommodated between the interface of Ile5-Tyr72-DNA. (d) Two water-mediated hydrogen bonds, involving water at Ile5-Tyr72 and DNA-water (green). The protein associated waters at the interface during this phase exchange (represented by two different waters entering and leaving the site, magenta and orange). (B) (a) Course of a water during the single water-mediated hydrogen bond for Sox18-DNA held by the hydroxyl of TyrY72, the lower plateau is the residency time for this water. Distances shown are for the water hydrogen atom to the acceptor oxygen atom. Water “barcode” showed as alternating colored (black and gray) represent different water molecules that occupy this site at the interface. “Barcode” highlights the single water-mediated hydrogen bond and two water-mediated hydrogen bond phase depicted by the maroon bar. Bottom panel represent trajectory of the same water (top panel) from the DNA where the bridging interaction at the interface. A similar “barcode” for water molecules at the DNA site are shown below the trace. (b) Structural representation of a single water-mediated hydrogen bond at interface of Ile5-Tyr72-DNA of Sox18-DNA complex. The protein and DNA oxygen atoms that form the bridging hydrogen bonds are shows as spheres. The average distance between the water hydrogen atom and respective oxygen atom in each plot is shown for the plateau highlighted. (c) Two water-mediated hydrogen bond at the interface of Ile5-Tyr72-DNA for Sox18-DNA. The Tyr and Ile associated water is in maroon and the DNA water in green. The trajectories of these waters are shown in the plots along with the corresponding “water barcodes.” The asterisk highlights distances close to the para-hydroxyl but not yet hydrogen bonded. (C) (a) Trajectory plots of a water for the Y72F variant Sox18 complex. The plateau indicates a “long-lived” water close to the para-carbon (C_ζ) of the Phe side chain. The “barcode” below the plot indicates water molecules that are found at this site relative to the Phe side chain for the duration of the simulation. The average distance of the para-carbon to the water for the plateau is listed. (b) Plot of the same water molecule as in (a) with respect to the DNA. The average distance of this water to the oxygen atom to its DNA hydrogen binding partner is listed. (b) Structural model of Y72F variant Sox18 complex. The Phe side chain is in red, the Ile side chain and the DNA base that are able to form hydrogen bonds to the water are shown as sticks. (c and d) Plots and models similar to (a and b), highlighting that a single-water motif for the variant simulation is observed through the entire 200 ns.

Per capita country-specific water requirements to fulfill hydrogen demand in 2020 and 2050: a solar and b onshore wind power production. The figure shows the water requirements to fulfill hydrogen demand a, b at country level as per capita water requirements and c, d in terms of total global water requirements in 2020 and 2050 based on a, c solar and b, d onshore wind power production. The countries are selected from the top 30 in terms of total hydrogen demand in 2050 and are ordered based on the amount of renewable available water. The interval bars represent the range of land required in 2050 based on the reference and the extreme scenarios of global hydrogen demand in 2050: 400 Mt/y (reference), 92 Mt/y (smallest), 646 Mt/y (largest). The gray areas represent the fractions of available water resources (water resources minus environmental flow requirements) in each country, corresponding to the water withdrawals. The red areas indicate water withdrawals exceeding the water availability limit (100%, 250%, and 500%). The purple, blue, and yellow stacks represent water withdrawals in agriculture, industry, and municipality, respectively. The red stacks represent the water required for hydrogen demand in 2020 and 2050. Total water withdrawals exceeding 100% indicate the presence of water scarcity.