l-Arginine reduces thioflavin T fluorescence but not fibrillation of bovine serum albumin

Liu, Kuan-Nan; Wang, Hsiang-Yun; Chen, Chih-Yuan; Wang, Steven S.‐S.

doi:10.1007/s00726-010-0536-0

Cited by 19 publications

(18 citation statements)

References 46 publications

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“…30–32 To confirm the Thioflavin T results, transmission electron micrographs (TEM) were taken of PAP 248–286 after a 96 hour incubation period. In the absence of either EGCG or GC, PAP 248–286 fibrillizes to form a dense network of amyloid fibers (Fig.…”

Section: Resultsmentioning

confidence: 99%

Site Specific Interaction of the Polyphenol EGCG with the SEVI Amyloid Precursor Peptide PAP(248–286)

Popovych¹,

Brender²,

Soong³

et al. 2012

J. Phys. Chem. B

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Recently, a 39 amino acid peptide fragment from prostatic acid phosphatase has been isolated from seminal fluid that can enhance infectivity of the HIV virus by up to four to five orders of magnitude. PAP(248–286) is effective in enhancing HIV infectivity only when it is aggregated into amyloid fibers termed SEVI. The polyphenol EGCG (epigallocatechin-3-gallate) has been shown to disrupt both SEVI formation and HIV promotion by SEVI, but the mechanism by which it accomplishes this task is unknown. Here we show that EGCG interacts specifically with the side-chains of monomeric PAP(248–286) in two regions (K251-R257 and N269-I277) of primarily charged residues, particularly lysine. The specificity of interaction to these two sites is contrary to previous studies on the interaction of EGCG with other amyloidogenic proteins, which showed the nonspecific interaction of EGCG with exposed backbone sites of unfolded amyloidogenic proteins. This interaction is specific to EGCG as the related gallocatechin (GC) molecule, which shows greatly decreased anti-amyloid activity, exhibits minimal interaction with monomeric PAP(248–286). The EGCG binding was shown to occur in two steps, with the initial formation of a weakly bound complex followed by a pH dependent formation of a tightly bound complex. Experiments in which the lysine residues of PAP(248–286) have been chemically modified suggest the tightly bound complex is created by Schiff-base formation with lysine residues. The results of this study could aid in the development of small molecule inhibitors of SEVI and other amyloid proteins.

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Section: Resultsmentioning

confidence: 99%

Site Specific Interaction of the Polyphenol EGCG with the SEVI Amyloid Precursor Peptide PAP(248–286)

Popovych¹,

Brender²,

Soong³

et al. 2012

J. Phys. Chem. B

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“…In the present work, we have illustrated the potential for obtaining false-positive results, using the effect that the free base l-arginine has on ThT, as an example. l-arginine has been shown to reduce Thioflavin T fluorescence but not protein fibrillation in (Liu et al 2010). However, in the work it is not indicated whether the pH of the final solutions containing arginine were monitored.…”

Section: Table 1 1 H Nmr Chemical Shifts and Assignments Of Tht In Nementioning

confidence: 90%

Effect of acidic and basic pH on Thioflavin T absorbance and fluorescence

et al. 2015

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Thioflavin T (ThT) is a fluorescent dye able to enhance significantly its fluorescence quantum yield upon binding to protein amyloids. ThT assay is widely used to detect and quantify amyloids in a variety of conditions, including solutions with different pH levels. In the present work, the effect of acidic and basic pH on the conformation of the ThT molecule and its absorption and fluorescence properties was studied. The results show that both acidic and basic pH decrease significantly the intensity of ThT absorption in the visible region and fluorescence emission intensity. Low pHs induce an immediate "all-or-nothing" decrease in the ThT signal, while in alkaline solutions the ThT signal decreases gradually over time. pH-induced signal quenching is less in the presence of glycerol or protein aggregates. Two different mechanisms are responsible for the ThT signal quenching-the ThT hydroxylation at basic pH and protonation of the nitrogen atom of the dimethylamino group at acidic pH. ThT assays should be carefully carried out at basic or acidic pH as strong pH dependence of ThT could be responsible for misinterpretation and false positive/negative experimental results. The potential unsuitability of ThT as a probe in solutions with high pH (>9) has been shown.

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“…In fact, ThT fluorescence intensity could potentially be affected by interactions between ThT and the osmolyte, which is always present at many thousand-fold higher concentrations than ThT, as well as by competitive osmolyte binding on the fibril surface [41,42]. Furthermore, osmolytes can induce fibrillar polymorphism, as we report for glucagon (see below).…”

Section: Introductionmentioning

confidence: 92%

The Effect of Osmolytes on Protein Fibrillation

Macchi

Eisenkolb

Kiefer

et al. 2012

IJMS

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Osmolytes are small molecules that are exploited by cells as a protective system against stress conditions. They favour compact protein states which makes them stabilize globular proteins in vitro and promote folding. Conversely, this preference for compact states promotes aggregation of unstructured proteins. Here we combine a brief review of the effect of osmolytes on protein fibrillation with a report of the effect of osmolytes on the unstructured peptide hormone glucagon. Our results show that osmolytes either accelerate the fibrillation kinetics or leave them unaffected, with the exception of the osmolyte taurine. Furthermore, the osmolytes that affected the shape of the fibrillation time profile led to fibrils with different structure as revealed by CD. The structural changes induced by Pro, Ser and choline-O-sulfate could be due to specific osmolytes binding to the peptides, stabilizing an otherwise labile fibrillation intermediate.

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l-Arginine reduces thioflavin T fluorescence but not fibrillation of bovine serum albumin

Cited by 19 publications

References 46 publications

Site Specific Interaction of the Polyphenol EGCG with the SEVI Amyloid Precursor Peptide PAP(248–286)

Site Specific Interaction of the Polyphenol EGCG with the SEVI Amyloid Precursor Peptide PAP(248–286)

Effect of acidic and basic pH on Thioflavin T absorbance and fluorescence

The Effect of Osmolytes on Protein Fibrillation

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