**3. Conclusion**

**2.5. Affinity of V-D2 to PrPc**

kinetics of V-D2 to Hu-rPrPc

amino acid fragment 109–112 of PrPc

96 A Critical Evaluation of Vitamin D - Clinical Overview

**Table 2.** Binding kinetics of V-D2 and V-D3 to Hu-rPrPc

**Figure 7.** Reactivity of mAbs against PrPc

dependent manner. The blue line indicates signals for PrPc

)(90–231), and after saturating PrPc

with V-D2. However, V-D3 showed no affinity for PrPc

**and c**), indicating that within the 3F4 epitope, PrPc

(Hu-rPrPc

PrPc

\* ND, not detected.

**(90–231), as a Biacore assay**

A Biacore assay indicates a high affinity of V-D2 for human recombinant cellular prion protein

(90–231) was shown in **Table 2** [52].

(90–231).

with V-D2 by ELISA. The 3F4 epitope on PrPc

(90–231) and the red line f PrPc

**Ligand Analyte** *K* **a (1/M)** *K* **d (M)**

(90–231) V-D3 ND\* ND\*

, V-D2 binding to PrPc

V-D2 6.17 e8 1.62 e-9

3F4 + V-D2 1.12 e8 8.95 e-9

(90–231) with the anti-3F4 antibody, specific for

(90–231) was responsible for the interaction

(90–231) was decreased (**Figure 6a**

(90–231) (**Figure 6b**), The binding

was affected by V-D2 in a dose-

(101–130).

We detected V-D2-induced Aβ40 oligomerization by QCM, and electron microscopic observation demonstrated the potential of V-D2 for Aβ40 oligomerization through β-sheet formation as revealed by Th-T study. V-D2-mediated Aβ40 oligomerization occurs through interaction between the Phe19 benzene ring of Aβ40 and the C22–C23 double bond of V-D2. In case of prion, the fragment of V-D2 binding to PrPc (90–231) is around 3F4 epitope, 109–112 amino acid in PrPc (90–231). These fragments are involved in the sensitive fragments to pH shifts and thermal stress. The binding of V-D2 to amyloidogenic peptides in brain might give some insights to oligomerization of these peptides in the brain.
