Analysis of biogenic carbonyl compounds in rainwater by stir bar sorptive extraction technique with chemical derivatization and gas chromatography-mass spectrometry

Stir bar sorptive extraction is a powerful technique for the extraction and analysis of organic compounds in aqueous matrices. Carbonyl compounds are ubiquitous components in rainwater, however, it is a major challenge to accurately identify and sensitively quantify carbonyls from rainwater due to the complex matrix. A stir bar sorptive extraction technique was developed to efficiently extract carbonyls from aqueous samples following chemical derivatization by O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride. Several commercial stir bars in two sizes were used to simultaneously measure 29 carbonyls in aqueous samples with detection by gas chromatography with mass spectrometry. A100 mL aqueous sample was extracted by stir bars and the analytes on stir barswere desorbed into a 2mLsolvent solution in an ultrasonic bath. The preconcentration Coefficient for different carbonyls varied between 30 and 45 times. The limits of detection of stir bar sorptive extraction with gas chromatography mass spectrometry for carbonyls (1030 ng/L) were improved by ten times compared with other methods such as gas chromatography with electron capture detection and stir bar sorptive extraction with high-performance liquid chromatography and mass spectrometry. The technique was used to determine carbonyls in rainwater samples collected in York, UK, and 20 carbonyl species were quantified including glyoxal, methylglyoxal, isobutenal, 2-hydroxy ethanal

Competition between α-actinin and Ca2+-Calmodulin Controls Surface Retention of the L-type Ca2+ Channel CaV1.2

Regulation of neuronal excitability and cardiac excitation-contraction coupling requires proper localization of L-type Ca2+ channels. We show that the actin-binding protein α-actinin binds to the C-terminal surface targeting motif of α11.2, the central pore-forming CaV1.2 subunit, to foster its surface expression. Disruption of α-actinin function by dominant negative or shRNA constructs reduces CaV1.2 surface localization in HEK293 and neuronal cultures, and dendritic spine localization in neurons. We demonstrate that calmodulin displaces α-actinin from their shared binding site on α11.2 upon Ca2+ influx through L-type channels but not through NMDAR, thereby triggering loss of CaV1.2 from spines. Coexpression of a Ca2+-binding deficient calmodulin mutant does not affect basal CaV1.2 surface expression, but inhibits its internalization upon Ca2+ influx. We conclude that α-actinin stabilizes CaV1.2 at the plasma membrane, and that its displacement by Ca2+-calmodulin induces Ca2+-induced endocytosis of CaV1.2, thus providing an important negative feedback mechanism for Ca2+ influx

Multi-Method Dispatch Using Multiple Row Displacement

Multiple Row Displacement (MRD) is a new dispatch technique for multi-method languages. It is based on compressing an n-dimensional table using an extension of the single-receiver row displacement mechanism. This paper presents the new algorithm and provides experimental results that compare it with implementations of existing techniques: compressed n-dimensional tables, look-up automata and single-receiver projection. MRD uses comparable space to the other techniques, but has faster dispatch performance

Multi-Method Dispatch Using Multiple Row

Multiple Row Displacement (MRD) is a new dispatch technique for multi-method languages. It is based on compressing an n-dimensional table using an extension of the single-receiver row displacement mechanism. This paper presents the new algorithm and provides experimental results that compare it with implementations of existing techniques: compressed n-dimensional tables, look-up automata and single-receiver projection. MRD uses comparable space to the other techniques, but has faster dispatch performance

Method Dispatch for Multi-Method Object-Oriented Languages

Two new techniques for multi-method dispatch are presented, both sufficiently general to apply to reflexive languages where methods and types can be added and removed at run-time. However, these techniques also apply to non-reflexive languages. One of the techniques operates by performing projections onto single-receiver dispatch tables, and thus benefits from existing research into single-receiver dispatch techniques. It provides method dispatch in O(k), where k is the arity of the method, and it is up to 6 times more space efficient than current table-based techniques. The second new technique does not provide constant-time dispatch, but has very low memory requirements and performs favorably against other techniques at a large percentage of call-sites. It is meant to be used as a replacement for inheritance lookup as the cache-miss algorithm in existing cache-based techniques. RESEARCH PAPER Subjects: language design and implementation Contact Author: Wade Holst Department of Comput..