Electrospray time-of-flight mass spectrometry of the intact MS2 virus capsid [15]

Journal of the American Chemical Society

Volumn 122, Issue 14, 2000, Pages 3550-3551

  Tito, Mark A ^a   Tars, Kaspar ^b   Valegard, Karin ^b   Hajdu, Janos ^b   Robinson, Carol V ^a  

^a UNIVERSITY OF OXFORD   (United Kingdom)

^b UPPSALA UNIVERSITY   (Sweden)

Author keywords

[No Author keywords available]

Indexed keywords

VIRUS PROTEIN;

BACTERIOPHAGE; LETTER; MASS SPECTROMETRY; NONHUMAN; PROTEIN ASSEMBLY; PROTEIN STRUCTURE; SIMULATION; VIRUS CAPSID; VIRUS TRANSMISSION;

EID: 0034639980     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja993740k     Document Type: Letter

References (21)

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12. 20 The MS2 capsid sample was dialyzed extensively using a Centricon C-100 (Amicon) at a concentration of 10 mM. Samples for analysis were introduced from aqueous solution (pH 7.1 ) at a concentration of 5 μM in the absence of buffer from a gold plated borosilicate nanoflow needle prepared in-house.'5
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14. 21
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17. To obtain the mass of Ihe virus capsid 50 acquisitions were signal averaged and a mean smoothing algorithm applied (2 × 25) (MassLynx version 3.2). The spectrum was imported into Win-IR (Bio-Rad/Galactic Industries Co., Salem, NH) and fitted with a linear baseline. The charge states over the mass range mlz 20147-24152.7 were modeled with Gaussian distributions. Masses were calculated from ml- values obtained for the center of the fitted peak. 21 consecutive Gausssian distributions were fitted with the exception of the peak between m/z 23809.0 and 24152.7, which could not be determined with confidence. From the two highest intensity consecutive m/z values in Figure Ib (21346.2 and 21142.4) the charges on the ions were assigned initially as 105 and 104 by the solution of simultaneous equations.16 Since this method does not take account of the difficulties in determining m/z values of very large molecular weight species the charge on the peaks was iterated across the series and the results of this process are shown in the Supporting Information. 12 charges were assigned to each m/z value and each series used to calculate the mass of the neutral molecule. The standard deviations of the 12 series showed that four charge state assignments had the lowest standard deviations, between 5010 and 5434. across the 21 peaks. Figure 2 and Supporting Information. From these four charge state assignments a value for the experimental mass was calculated as 2484700 ± 25200 Da. It is important to note that this mass was calculated from the peak tops of the highest charge states in the series and does not therefore take into account the natural asymmetry of the peaks and the increased counterions that bind to the lower charge slates.
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