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Recent evidence has shown a correlation between the heat diffusion pathways and the known allosteric communication pathways in proteins. Allosteric communication in proteins is a central, yet unsolved, problem in biochemistry, and the study and characterization of the structural determinants that mediate energy transfer among different parts of proteins is of major importance. In this work, we characterized the role of hydrogen bonds in diffusivity of thermal energy for two sets of α-helices with different abilities to form hydrogen bonds. These hydrogen bonds can be a constitutive part of the α-helices or can arise from the lateral chains. In our in vacuo simulations, it was observed that α-helices with a higher possibility of forming hydrogen bonds also had higher rates of thermalization. Our simulations also revealed that heat readily flowed through atoms involved in hydrogen bonds. As a general conclusion, according to our simulations, hydrogen bonds fulfilled an important role in heat diffusion in structural patters of proteins.

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Within the SIM RMO, certain NMIs/ DIs have indicated the need to demonstrate their measurement capability for the determination of ethanol in aqueous matrices. Reflecting upon the current situation, the SIM Chemical Metrology Working Group (CMWG) conducted a second regional Key Comparison in 2016 linked to the CCQM-K27, SIM.QM-K27. The RMO Key Comparison SIM.QM-K27 was coordinated by INMETRO, who demonstrated capability in the CCQM-K27.2 subsequent study: determination of ethanol in aqueous media. INMETRO also coordinated the first SIM RMO Key Comparison SIM.QM-K1. For SIM.QM-K27, two levels of ethanol in water solutions were gravimetrically prepared by INMETRO with a concentration range between 0.5 mg/g and 5 mg/g. The gravimetric value of the aqueous ethanol solutions was used to link SIM.QM-K27 to the CCQM-K27 Key comparison reference value (KCRV). The gravimetric values for SIM.QM-K27 Level 1 and Level 2 were (0.814 ± 0.008) mg/g (U k =2 ) and (3.818 ± 0.038) mg/g (U k =2 ), respectively. The KCRV was determined using the purity-corrected gravimetric preparation values. The KCRV uncertainty was assigned as 1 % from the reference values in order to give the same uncertainty as in the CCQM-K27.2 comparison. Fourteen laboratories took part in this regional KC, from SIM and other RMOs. One participant (INACAL) did not send results and thus it's capability was not evaluated. Ten of the thirteen participants in the SIM.QM-K27 demonstrated their ability to measure ethanol in aqueous matrix in the concentration range of 0.5 mg/g to 5 mg/g (both levels). One participant (ISP) demonstrated its ability to measure ethanol in aqueous matrix only at the low level (0.5 to 1.5 mg/g) and another participant (INM) demonstrated its ability to measure ethanol in aqueous matrix only at the high level (1.5 to 5.0 mg/g). NIMT did not demonstrate its ability to measure ethanol in aqueous matrix from 0.5 mg/g to 5 mg/g (both levels). The abilities demonstrated by the participants should be indicative of their ability to provide reference measurements for ethanol content in aqueous samples for both forensic and commodities applications. This report presents the results of the SIM Key comparison SIM.QM-K27. Successful participation in SIM.QM-K27 demonstrates the following measurement capabilities in determining mass fraction of ethanol in mass fraction range from 0.5 mg/g to 5 mg/g in an aqueous matrix. KEY WORDS FOR SEARCH Key comparison and ethanol in water Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

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