Non-linear dose-response relation between urinary levels of nicotine and its metabolites and cognitive impairment among an elderly population in China.

BACKGROUND: Active smoking and exposure to environmental tobacco smoke may be related to cognitive function decline. We assessed the associations of urinary levels of nicotine and its metabolites with cognitive function. METHODS: A total of 553 elder adults at high risk of cognitive impairment and 2212 gender- and age-matched individuals at low risk of cognitive impairment were selected at a ratio of 1: 4 from the remained individuals (n = 6771) who completed the baseline survey of the Shenzhen Ageing-Related Disorder Cohort, after excluding those with either Alzheimer's disease, Parkinson's syndrome or stroke as well as those with missing data on variables (including active and passive smoking status, Mini-Cog score). Urinary levels of nicotine and its metabolites and cognitive function for all individuals were measured by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) and assessed using the Mini-Cog test, respectively. Associations of urinary levels of nicotine and its metabolites with cognitive function were analyzed by conditional logistic regression models. RESULTS: Individuals in the highest tertile of urinary OHCotGluc (OR: 1.52, 95%CI: 1.19-1.93) or NNO (OR: 1.50, 95%CI: 1.16-1.93) levels as well as in the second tertile of urinary ∑Nic level (OR: 1.43, 95%CI: 1.13-1.82) were at higher risk of cognitive impairment compared with those in the corresponding lowest tertile. Restricted cubic spline models revealed the non-linear dose-response relationships between urinary levels of OHCotGluc, NNO or ∑Nic and the risk of cognitive impairment. CONCLUSIONS: Urinary levels of OHCotGluc, NNO or ∑Nic exhibited a non-linear dose-response relationship with cognitive function in the urban elderly.

Importance of the ionic nature of ionic liquids in affecting enzyme performance.

The activity and stability of mushroom tyrosinase were studied in ionic liquid (IL)-containing aqueous systems. The effect of three ILs ([BMIm][PF(6)], [BMIm][BF(4)]), and [BMIm][MeSO(4)], where [BMIm] = 1-butyl-3-methylimidazolium) and their inorganic salts (KMeSO(4), KPF(6), and NaBF(4)) on the enzyme performance was investigated by comparing the kinetic (such as K(m), V(max), optimal pH and temperature, and activation energy) and thermostability parameters (including half-lives, deactivation constants, activation energies for enzyme deactivation, DeltaG*, DeltaH*, and DeltaS*) of the enzyme in the absence and presence of the ILs and their anions. Both the three ILs and their inorganic salts were able to trigger enzyme activation. The enzyme could be stabilized by addition of KMeSO(4) and NaBF(4) but destabilized by the presence of all the three ILs. The substrate selectivity of the enzyme was unchanged. The effect of ILs on enzyme performance can be largely attributed to their ionic nature via interaction with the enzyme structure, the substrate, and the water molecules associated with the enzyme, depending on their kosmotropocity, nucleophilicity, and H-bond basicity. The different influences brought from the ILs and their associated ions indicate the cooperative functioning of both cation and anion of the IL in affecting the enzyme performance.

Tyrosinase activity in ionic liquids.

Activity of mushroom tyrosinase was studied in three ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF(6)]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF(4)]) and 1-butyl-3-methylimidazolium methylsulfate ([BMIm][MeSO(4)]), and was compared to that in chloroform. Kinetic parameters of the enzyme were determined and the results indicate that the enzyme in ionic liquids basically follows the same catalytic mechanism as in water, and that the ionic liquids may affect the enzyme activity by direct interacting with the enzyme and thus hindering the E-S binding due to their high hydrophilicity and polarity.