On the Security and Performance of Proof of Work Blockchains

Proof of Work (PoW) powered blockchains currently account for more than 90% of the total market capitalization of existing digital currencies. Although the security provisions of Bitcoin have been thoroughly analysed, the security guarantees of variant (forked) PoW blockchains (which were instantiated with different parameters) have not received much attention in the literature. In this paper, we introduce a novel quantitative framework to analyse the security and performance implications of various consensus and network parameters of PoW blockchains. Based on our framework, we devise optimal adversarial strategies for double-spending and selfish mining while taking into account real world constraints such as network propagation, different block sizes, block generation intervals, information propagation mechanism, and the impact of eclipse attacks. Our framework therefore allows us to capture existing PoW-based deployments as well as PoW blockchain variants that are instantiated with different parameters, and to objectively compare the tradeoffs between their performance and security provisions

Modified Peptides as Indicators for Thermal and Nonthermal Reactions in Processed Milk

Site-specific relative quantification of β-lactoglobulin modifications in heated milk and dairy products was performed to determine their thermal and nonthermal origins and to evaluate marker candidates for milk processing. Therefore, formation kinetics of 19 different structures at 26 binding sites were analyzed by ultrahigh-performance liquid chromatography–tandem mass spectrometry with multiple reaction monitoring (UHPLC-MS/MS/MRM) after specific protein hydrolysis. The results indicate that (i) site-specific analysis of lactulosyllysine may be a more sensitive marker for mild heat treatment than its overall content; (ii) <i>N</i>^ε-carboxymethyllysine, N-terminal ketoamide, and asparagine deamidation are of thermal origin and may be good markers for rather intensive heat treatment, whereas <i>N</i>^ε-carboxyethyllysine reflects thermal and nonthermal processes; (iii) the relevance of methylglyoxal-derived arginine modifications is low compared to that of other modifications; (iv) oxidation of methionine and cysteine is a rather weak indicator of thermal impact; and (v) the tryptophan modifications formylkynurenine and kynurenine are of nonthermal origin and further degraded during processing

Comprehensive Analysis of Nonenzymatic Post-Translational β‑Lactoglobulin Modifications in Processed Milk by Ultrahigh-Performance Liquid Chromatography–Tandem Mass Spectrometry

Nonenzymatic post-translational protein modifications (nePTMs) result in changes of the protein structure that may severely influence physiological and technological protein functions. In the present study, ultrahigh-performance liquid chromatography–electrospray ionization tandem mass spectrometry (UHPLC–ESI-MS/MS) was applied for the systematic identification and site-specific analysis of nePTMs of β-lactoglobulin in processed milk. For this purpose, β-lactoglobulin, which had been heated with lactose under conditions to force nePTM formation (7 d/60 °C), was screened for predicted modifications by using full scans and enhanced resolution scan experiments combined with enhanced product ion scans. Thus, the main glycation, glycoxidation, oxidation, and deamidation products of lysine, arginine, methionine, cysteine, tryptophan, and asparagine, as well as the N-terminus, were identified. Using these MS data, a very sensitive scheduled multiple reaction monitoring method suitable for the analysis of milk products was developed. Consequently, 14 different PTM structures on 25 binding sites of β-lactoglobulin were detected in different milk products

Nonenzymatic β‑Carotene Degradation in Provitamin A‑Biofortified Crop Plants

Provitamin A biofortification, the provision of provitamin A carotenoids through agriculture, is regarded as an effective and sustainable intervention to defeat vitamin A deficiency, representing a global health problem. This food-based intervention has been questioned in conjunction with negative outcomes for smokers and asbestos-exposed populations of the CARET and ATBC trials in which very high doses of β-carotene were supplemented. The current notion that β-carotene cleavage products (apocarotenoids) represented the harmful agents is the basis of the here-presented research. We quantitatively analyzed numerous plant food items and concluded that neither the amounts of apocarotenoids nor β-carotene provided by plant tissues, be they conventional or provitamin A-biofortified, pose an increased risk. We also investigated β-carotene degradation pathways over time. This reveals a substantial nonenzymatic proportion of carotene decay and corroborates the quantitative relevance of highly oxidized β-carotene polymers that form in all plant tissues investigated