Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 5 de 5
Filter
Add more filters










Database
Language
Publication year range
1.
Article in English | MEDLINE | ID: mdl-30601713

ABSTRACT

Swiss control authorities checked the safety assessment of nine major producers of polyolefin granulates for making food contact materials. It was a pilot project to gain experience on the procedure of collecting and evaluating compliance documentation, but also to obtain insight into the quality of compliance work performed by the main plastic producers. It revealed that there are fundamental problems in performing such control. These are reported with proposals for improvement. For most products, the safety assessment made available did not correspond to the requirements, as confirmed by a group of internationally recognised experts, who were asked for their opinion on whether the safety of the migrates was assessed in accordance to 'internationally accepted scientific methods on risk assessment', as required by Art. 19 of Regulation (EU) 10/2011 and specified by EFSA.


Subject(s)
Food Contamination/analysis , Food Safety , Polyenes/analysis , Documentation , European Union , Food Packaging , Humans , Risk Assessment , Switzerland
2.
Anal Bioanal Chem ; 383(6): 895-902, 2005 Nov.
Article in English | MEDLINE | ID: mdl-16254719

ABSTRACT

Two different strategies for coupling liquid chromatography with atmospheric pressure matrix assisted laser desorption/ionization (AP MALDI) are presented. The first method is flow-injection liquid AP UV-MALDI. Compared with previous similar research, the detection limit was improved 10 times to 8.3 fmol using a solution of 50 nM peptide with 25 mM alpha-cyano-4-hydroxycinnamic acid. The applicability of this method to measure oligosaccharides, actinomycin antibiotics, antibiotics, phosphopeptides, and proteins is demonstrated. The upper mass limit achieved with the current instrumentation is 6,500 Da (doubly charged cytochrome c). The feasibility of a second strategy based on single-droplet IR AP MALDI is demonstrated here. Aqueous peptide solutions were successfully measured by this method.


Subject(s)
Atmospheric Pressure , Chromatography, Liquid/instrumentation , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/instrumentation , Chromatography, Liquid/methods , Coumaric Acids/pharmacology , Flow Injection Analysis/methods , Peptides/pharmacology , Propionates , Sensitivity and Specificity , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods
3.
Analyst ; 129(7): 574-8, 2004 Jul.
Article in English | MEDLINE | ID: mdl-15213821

ABSTRACT

A new technique is presented for the coupling of atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) mass spectrometry with liquid delivery systems. Mass measurements of polymers and peptides are demonstrated using a co-dissolved matrix, e.g. alpha-cyano-4-hydroxycinnamic acid (HCCA). Improvements in terms of sensitivity are achieved by optimizing the shape und control of the exit capillary and by using a laser (355 nm) at a 1 kHz repetition rate. Two calibration experiments promise a good applicability of the presented coupling method for quantitative measurements. The limit of detection achieved so far is 500 nM for peptides in methanol solution containing 25 mM HCCA.


Subject(s)
Proteins/analysis , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods , Animals , Flow Injection Analysis
4.
J Am Soc Mass Spectrom ; 14(12): 1470-6, 2003 Dec.
Article in English | MEDLINE | ID: mdl-14652193

ABSTRACT

Electrospray time-of-flight mass spectrometry was used to quantitatively determine the dissociation constant of chorismate mutase and a transition state analogue inhibitor. This system presents a fairly complex stoichiometry because the native protein is a homotrimer with three equal and independent substrate binding sites. We can detect the chorismate mutase trimer as well as chorismate mutase-inhibitor complexes by choosing appropriate conditions in the ESI source. To verify that the protein-inhibitor complexes are specific, titration experiments with different enzyme variants and different inhibitors were performed. A plot of the number of bound inhibitors versus added inhibitor concentration revealed saturation behavior with 3:1 (inhibitor:functional trimer) stoichiometry for the TSA. The soft ESI conditions, the relatively high protein mass of 43.5 kDa, and the low charge state (high m/z) result in broad peaks, a typical problem in analyzing noncovalent protein complexes. Due to the low molecular weight of the TSA (226 Da) the peaks of the free protein and the protein with one, two or three inhibitors bound cannot be clearly resolved. For data analysis, relative peak areas of the deconvoluted spectra of chorismate mutase-inhibitor complexes were obtained by fitting appropriate peak shapes to the signals corresponding to the free enzyme and its complexes with one, two, or three inhibitor molecules. From the relative peak areas we were able to calculate a dissociation constant that agreed well with known solution-phase data. This method may be generally useful for interpreting mass spectra of noncovalent complexes that exhibit broad peaks in the high m/z range.


Subject(s)
Chorismate Mutase/antagonists & inhibitors , Enzyme Inhibitors/chemistry , Bacillus subtilis/enzymology , Chorismate Mutase/genetics , Escherichia coli/enzymology , Escherichia coli/genetics , Kinetics , Spectrometry, Mass, Electrospray Ionization
5.
J Am Soc Mass Spectrom ; 14(5): 442-8, 2003 May.
Article in English | MEDLINE | ID: mdl-12745213

ABSTRACT

Noncovalent complexes between chicken muscle adenylate kinase and two inhibitors, P(1),P(4)-di(adenosine-5')tetraphosphate (Ap4A) and P(1),P(5)-di(adenosine-5') pentaphosphate (Ap5A), were investigated with electrospray ionization mass spectrometry under non-denaturing conditions. The nonconvalent nature and the specificity of the complexes are demonstrated with a number of control experiments. Titration experiments allowed the association constants for inhibitor binding to be determined. Problems with concentration dependent ion yields are circumvented by a data evaluation method that is insensitive to the overall ionization efficiency. The K(a) values found were 9.0 x 10(4) M(-1) (Ap4A) and 4.0 x 10(7) M(-1) (Ap5A), respectively, in very good agreement with available literature data.


Subject(s)
Adenylate Kinase/antagonists & inhibitors , Adenylate Kinase/chemistry , Enzyme Inhibitors/chemistry , Spectrometry, Mass, Electrospray Ionization , Animals , Chickens , Molecular Structure , Muscle, Skeletal/enzymology , Protein Binding
SELECTION OF CITATIONS
SEARCH DETAIL
...