A Mass Spectrometric Solution to the Address Problem of Combinatorial Libraries

Brummel, Christopher L.; Lee, Irene N. W.; Zhou, Ying; Benkovic, Stephen J.; Winograd, Nicholas

doi:10.1126/science.8153627

Cited by 141 publications

(70 citation statements)

References 25 publications

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“…They corresponded to the protonated and deprotonated molecules as well as to the immonium ion. Such data confirmed published results by Winograd et al 17 who analyzed adsorbed phenylalanine on polystyrene by TOF-SIMS and obtained the protonated molecule and the immonium ion with noticeable abundances. The similarity between these two spectra suggests that the ionic bond is broken quite easily which was expected from Cooks studies 10 who showed that preformed ions are intense in desorption mass spectra.…”

Section: Resultssupporting

confidence: 93%

Time-of-flight secondary ion mass spectrometry of Fmoc-amino acids linked to solid supports through ionic interactions

Enjalbal¹,

Martínez²,

Subra³

et al. 1998

Rapid Commun. Mass Spectrom.

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The TOF-SIMS (time-of-flight-secondary ion mass spectrometry) spectra of Fmoc-amino acids linked to solid supports through ionic interactions have been studied to examine if easy desorption of preformed ions from the surface occurred. Preliminary results indicated that the structure of the polymer affected the nature of the recovered ions. However, in the case of widely used polystyrene based supports, characteristic ions of the amino acids were clearly observed with noticeable abundances. Moreover, an analytical criterion to differentiate Fmoc-amino acids linked to various solid supports through either covalent or ionic bonds was established. # 1998 John Wiley & Sons, Ltd. Received 9 September 1998; Accepted 9 September 1998 Very few spectroscopic methods are available to analyze samples in the solid state whereas such techniques present numerous applications in the fast-growing field of solidphase chemistry. Indeed, rapid and efficient product characterization should be obtained with the organic moieties still anchored to the support, thus avoiding product release in solution by any time-consuming and eventually deleterious chemical treatments.Cross polarization-magic angle spinning (CP-MAS) NMR 1 and IR 2 have been used to follow polymer supported syntheses but the main drawback of such techniques consists of the overlapping of the polymer signals with the signals of the expected compound.We have developed an alternative analytical method based on time-of-flight-secondary ion mass spectrometry (TOF-SIMS) to monitor step by step solid-phase peptide syntheses. 3,4 We report the results obtained when this technique was applied to samples where the amino acids were not covalently linked as previously described but simply anchored onto various supports through ionic interactions. EXPERIMENTAL ChemicalsProtected amino acids and the MBHA-resin were purchased from Senn Chemicals AG (Germany). The pin support consists of a derivatized crown, upon which synthesis is performed, and an inert polypropylene stem. The aminomethylated polystyrene-grafted (PS-pin) and methacrylic acid/dimethylacrylamide-grafted (MD-pin) crowns were supplied by Chiron Technologies Pty. Ltd. (Australia). The crowns and the resin which bear free amino groups were immersed overnight in a 0.4 M dimethylformamide (DMF) solution of Fmoc-protected amino acid (either Fmoc-Phe-OH or Fmoc-Leu-OH) and then washed once with DMF for 1 minute. Mass spectrometryCrown samples analyzed by TOF-SIMS were cut out directly from the the pins with a razor blade to obtain thin slices, which were then immediately placed on a stainless grid. The resin beads were analyzed directly, as such. TOF-SIMS measurements were performed on a TRIFT I spectrometer from the PHI-Evans Company (Eden-Prairie, MN, USA). Spectra were recorded using a pulse (1 ns, 12 kHz) liquid metal source ( 69 Ga, 15 keV) operating in the bunched mode of operation in order to provide good mass resolution (m/Dm = 2000, measured at m/z 43). Due to large charging effects on the insulating materials pres...

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Section: Resultssupporting

confidence: 93%

Time-of-flight secondary ion mass spectrometry of Fmoc-amino acids linked to solid supports through ionic interactions

Enjalbal¹,

Martínez²,

Subra³

et al. 1998

Rapid Commun. Mass Spectrom.

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“…While it is possible to synthesize mixtures of small molecules each in a tiny amount, determining the identity of ''winners'' is accomplished by a process of deconvolution rather than encoding. [This is because the only code in such a library is chemical identity, and at such tiny amount the only tool useful to establish identity is mass spectrometry (3)(4)(5)(6)(7)(8).] Instead, such small molecule libraries are produced on polymer beads, each bead possessing only one type of molecule (9).…”

Section: Encoding Strategies In Combinatorial Chemistrymentioning

confidence: 99%

Encoding strategies in combinatorial chemistry

Czarnik

1997

Proc. Natl. Acad. Sci. U.S.A.

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“…Presuming that this hydrogen bond might be at least 15-10-_. 5 (36), although a generic screen using surface ionization techniques may eventually prove feasible (37).…”

Section: Application Of the Proton Inventory Technique To Antibody Camentioning

confidence: 99%

Dissection of an antibody-catalyzed reaction.

Stewart

Krebs

Siuzdak

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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Antibody 43C9 accelerates the hydrolysis of a p-nitroanilde by a factor of 2.5 x 10i over the background rate in addition to catalyzing the hydrolysis of a series of aromatic esters. Since this represents one of the largest rate accelerations achieved with an antibody, we have undertaken a series of studies aimed at uncovering the catalytic mechanism of 43C9. The immunogen, a phosphonamidate, was designed to mimic the geometric and electronic characteristics of the tetra- Fig. 1. The data can be fit either to a reaction mechanism involving the titration of a group at the antigenbinding site whose dissociation promotes substrate hydrolysis or to one that features a change in the rate-limiting step around a central antibody-bound intermediate species due to changes in pH. For the p-nitrophenyl ester, the rate constant for p-nitrophenol release (measured independently) approximates ku in the pHindependent region (pH > 9). Thus, the apparent pKa of 9 found for both substrates in the pH rate profiles cannot be due to dissociation of a common acidbase group involved in binding or catalysis. Further support for this conclusion obtains from the absence of pH-dependent binding of 1, a competitive inhibitor ofester hydrolysis that should be sensitive to the ionization state of an active-site acid-base group. The 104 difference in kcw at pH > 9.0 between the two substrates also rules out any mechanism involving a shared conformational change step STo whom reprint requests should be addressed.

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A Mass Spectrometric Solution to the Address Problem of Combinatorial Libraries

Cited by 141 publications

References 25 publications

Time-of-flight secondary ion mass spectrometry of Fmoc-amino acids linked to solid supports through ionic interactions

Time-of-flight secondary ion mass spectrometry of Fmoc-amino acids linked to solid supports through ionic interactions

Encoding strategies in combinatorial chemistry

Dissection of an antibody-catalyzed reaction.

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