Hsp70s mediate protein folding, translocation, and macromolecular complex remodeling reactions. Their activities are regulated by proteins that exchange ADP for ATP from the nucleotide-binding domain (NBD) of the Hsp70. These nucleotide exchange factors (NEFs) include the Hsp110s, which are themselves members of the Hsp70 family. We report the structure of an Hsp110:Hsc70 nucleotide exchange complex. The complex is characterized by extensive protein:protein interactions and symmetric bridging interactions between the nucleotides bound in each partner protein's NBD. An electropositive pore allows nucleotides to enter and exit the complex. The role of nucleotides in complex formation and dissociation, and the effects of the protein:protein interactions on nucleotide exchange, can be understood in terms of the coupled effects of the nucleotides and protein:protein interactions on the open-closed isomerization of the NBDs. The symmetrical interactions in the complex may model other Hsp70 family heterodimers in which two Hsp70s reciprocally act as NEFs.

It has been widely accepted that the primary function of the Lands cycle is to provide a route for acyl remodeling to modify fatty acid (FA) composition of phospholipids derived from the Kennedy pathway. Lysophosphatidylcholine acyltransferase (LPCAT) is an evolutionarily conserved key enzyme in the Lands cycle. In this study, we provide direct evidence that the Arabidopsis thaliana LPCATs, LPCAT1 and LPCAT2, participate in the Lands cycle in developing seeds. In spite of a substantially reduced initial rate of nascent FA incorporation into phosphatidylcholine (PC), the PC level in the double mutant lpcat1 lpcat2-2 remained unchanged. LPCAT deficiency triggered a compensatory response of de novo PC synthesis and a concomitant acceleration of PC turnover that were attributable at least in part to PC deacylation. Acyl-CoA profile analysis revealed complicated metabolic alterations rather than merely reduced acyl group shuffling from PC in the mutant. Shifts in FA stereospecific distribution in triacylglycerol of the mutant seed suggested a preferential retention of saturated acyl chains at the stereospecific numbering (sn)-1 position from PC and likely a channeling of lysophosphatidic acid, derived from PC, into the Kennedy pathway. Our study thus illustrates an intricate relationship between the Lands cycle and the Kennedy pathway.

Sulfate radical (SO4 •–)- and hydroxyl radical (HO•)-based advanced oxidation processes (AOPs) are effective for the removal of organic pollutants in water treatment. This study compared the interactions of SO4 •– and HO• for the transformation of phenol in UV/peroxydisulfate (PDS) and UV/H2O2 with the presence of NO2 –, which is widely present in aquatic environments and transforms SO4 •– and HO• to •NO2. By using laser flash photolysis, the products of phenol reacting with SO4 •– and HO• were demonstrated to be phenoxy radical and phenol-HO-adduct radical, respectively. This result, along with density functional theory (DFT) calculations, indicate that the predominant reaction mechanisms of phenol with SO4 •– and HO• with phenol are electron transfer and addition, respectively. The different mechanisms induced the much higher formation of nitrophenols by SO4 •– than HO• in the presence of NO2 – through the fast combination of phenoxy radicals and •NO2. The conversion yields of phenol to nitrophenols (including 2-nitrophenol and 4-nitrophenol), were 47.5% by SO4 •– versus 5.3% by HO• at the experimental conditions. Increasing PDS/H2O2 dosages from 0.2 to 1 mM resulted in a 61.9% increase of nitrophenol conversion yield in UV/PDS/NO2 – but a 35.4% decrease of that in UV/H2O2/NO2 –. In addition, the significant formation of phenoxy radicals by SO4 •– also induced many nitrated polymers in UV/PDS/NO2 –, while those induced in UV/H2O2/NO2 – were negligible. The significant formation of nitrophenols and nitrated polymers increased the mutagenicity by 860.5% when the removal rate of phenol was 98% by UV/PDS/NO2 –. This is the first study to demonstrate the different mechanisms of phenol transformation by SO4 •– and HO• in the presence of NO2 –.

UV irradiation and chlorination have been widely used for water disinfection. However, there are some limitations, such as the risk of generating viable but nonculturable bacteria and bacteria reactivation when using UV irradiation or chlorination alone. This study comprehensively evaluated the feasibility of the UV/chlorine process in drinking water disinfection, and Pseudomonas aeruginosa was selected as the target microorganism. The number of culturable cells was effectively reduced by more than 5 orders of magnitude (5-log 10 ) after UV, chlorine, and UV/chlorine treatments. However, intact and VBNC cells were detected at 10 3 to 10 4 cells/mL after UV and chlorine treatments, whereas they were undetectable after UV/chlorine treatment due to the primary contribution of reactive chlorine species (Cl • , Cl 2•− , and ClO • ). After UV/chlorine treatment, the metabolic activity determined using single cell Raman spectroscopy was much lower than that after UV. The level of toxic opr gene in P. aeruginosa decreased by more than 99% after UV/chlorine treatment. Importantly, bacterial dark reactivation was completely suppressed by UV/chlorine treatment but not UV or chlorination. This study suggests that the UV/chlorine treatment can completely damage bacteria and is promising for pathogen inactivation to overcome the limitations of UV and chlorine treatments alone.