Dataset Information

A mix-and-click method to measure amyloid-? concentration with sub-micromolar sensitivity.

ABSTRACT: Aggregation of amyloid-? (A?) protein plays a central role in Alzheimer's disease. Because protein aggregation is a concentration-dependent process, rigorous investigations require accurate concentration measurements. Owing to the high aggregation propensity of A? protein, working solutions of A? are typically in the low micromolar range. Therefore, an ideal A? quantification method requires high sensitivity without sacrificing speed and accuracy. Absorbance at 280?nm is frequently used to measure A? concentration, but the sensitivity is low with only one tyrosine and no tryptophan residues in the A? sequence. Here we present a fluorescence method for A? quantification using fluorescamine, which gives high fluorescence upon reaction with primary amines. We show that, using hen egg white lysozyme as a standard, fluorescence correlates linearly with primary amine concentration across a wide range of fluorescamine concentrations, from 62.5 to 1000?µM. The maximal sensitivity of detection is achieved at a fluorescamine concentration of 250?µM or higher. The fluorescamine method is compatible with the presence of dimethyl sulfoxide, which is commonly used in the preparation of A? oligomers, and limits the use of absorbance at 280?nm due to its high background reading. Using aggregation kinetics, we show that the fluorescamine method gives accurate concentration measurements at low micromolar range and leads to highly consistent aggregation data. We recommend the fluorescamine assay to be used for routine and on-the-fly concentration determination in A? oligomerization and fibrillization experiments.

SUBMITTER: Xue C

PROVIDER: S-EPMC5579099 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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A mix-and-click method to measure amyloid-β concentration with sub-micromolar sensitivity.

Xue Christine C Lee Yoon Kyung YK Tran Joyce J Chang Dennis D Guo Zhefeng Z

Royal Society open science 20170809 8

Aggregation of amyloid-β (Aβ) protein plays a central role in Alzheimer's disease. Because protein aggregation is a concentration-dependent process, rigorous investigations require accurate concentration measurements. Owing to the high aggregation propensity of Aβ protein, working solutions of Aβ are typically in the low micromolar range. Therefore, an ideal Aβ quantification method requires high sensitivity without sacrificing speed and accuracy. Absorbance at 280 nm is frequently used to measu ...[more]

PMID: 28878984

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Project description:ContextImproving contraceptive method choice is a goal of international family planning. Method mix-the percentage distribution of total contraceptive use across various methods-reflects both supply (availability of affordable methods) and demand (client preferences). We analyze changes in method mix, regional contrasts, and the relationship of the mix to contraceptive prevalence.MethodsWe use 789 national surveys from the 1960s through 2019, from 113 developing countries with at least 1 million people and with data on use of 8 contraceptive methods. Two measures assess the "evenness" of the mix: method skew (more than 50% use is by 1 method), and the average deviation (AD) of the 8 methods' shares from their mean value. Population weighted and unweighted results are compared because they can differ substantially.ResultsUse of traditional methods has declined but still represents 11% of all use (population weighted) or 17% (unweighted country average). Vasectomy's share was historically low with the exception of a few countries but is now even lower. The previous trend toward greater overall evenness in the mix has slowed recently. Sub-Saharan Africa shows a hormonal method progression from oral contraceptives to injectables to implants in a substantial number of countries. In some countries with high HIV prevalence, the condom share has increased. The leading method's share differs by region: female sterilization in Asia (39%) and in Latin America (31%), the pill in the Middle East/North Africa (32%), and the injectable in sub-Saharan Africa (36%). Method skew persists in 30% of countries. "Evenness" of mix is not related to contraceptive prevalence.ConclusionThe marked diversity in predominant methods underscores the conclusion that no single method mix is ideal or appropriate everywhere. But that diversity across countries, coupled with the persisting high degree of extreme skewness in many of them, argues for continued concerted efforts for programs to increase method choice.

Dataset Information

A mix-and-click method to measure amyloid-? concentration with sub-micromolar sensitivity.

Publications

A mix-and-click method to measure amyloid-β concentration with sub-micromolar sensitivity.

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