Table 1 Tannin-PRP binding specificity

[48]

NMR

B2, PGG, TGG, PAC monomer, epicatechin

yes

40 mM B2, other assays 50 mM; either 0.5 ml of 2 mM or 4 mM PRP from mouse; pH 3.8

N-terminal proline residues linked to amide and amino structures bind tannin, then secondary interactions with galloyl groups changes structure of open conformation around PRP (specific binding)

Yes

[49]

NMR

PAC as B1, B3, C2

No

0.5-20 mM PRP (IB9) with 15.7 mM tannin; pH 3.5

Tannin-PRP binding is specific to a certain concentration of tannin; then becomes random

Yes

[50]

ESI-MS

EgCG, ECG, B2, B2 3-O gallate, reserpine

No

1:10 ratio protein: polyphenol; pH 3.2

Tannin-PRP binding is specific; PRP-reserpine did not bind (similar structure to studied tannins)

Yes

[51]

ESI-MS; DLS, SAXS

EgCG

No

0.336 mM (1–3.5 mg/ml) PRP (IB5); 2:1 protein: polyphenol; pH 5.5

Tannin-PRP interaction is specific and dependent on tannin interactions; PRP sites for tannin binding are independent and have free energy; at a threshold, multidendate tannin crosslinks strengthen tannin-PRP bonds

Yes

[43]

DLS, ITC

EgCG

No

6.4 or 12.8 EgCG with 0.25–2 mg IB5; pH 3.5

Tannin-PRP interaction is concentration dependent; there is slow and specific binding of tannins followed by rapid and non-specific aggregation as tannin-PRP binding sites are saturated.

Yes

[52]

In vitro digestion, SDS-PAGE, HPLC

EgCG

No

0.05–0.5 mM EgCG, Human salivary PRPs; protein: tannin ratio 3:1; pH gastric 2.07; duodenal pH 7.8

Preferential tannin-PRP binding compared to lipase, alpha amylase, chymotrypsin, trypsin, lactase

Yes

[86]

DLS, ITC

EgCG

No

1:5 ratio saliva: wine in 1% TFA compared to physiological conditions

Salivary PRP ‘moderately’ bound tannins

Yes

[47]

NMR, DLS

EgCG, EGC, PGG

Yes

20 mM polyphenol with 2 mM mouse PRP; pH 3.8

There is preferential binding of tannin to proline residues of PRPs vs. alternative amino acids

Yes