DESCRIPTION

CTSD (Cathepsin D) also named CPSD, is a representative aspartic proteinase in lysosomes and is widely distributed in various tissue cells of mammals. The expression level of CTSD varies depending on the tissue, whereas neurons in CNS tissues possess abundant CTSD. CTSD is synthesized as a 52-kDa precursor that is converted into an active ~48-kDa single-chain intermediate in the endosomes, and then into a fully active mature form, composed of a 28-kDa heavy chain and a 14-kDa light chain, in the lysosomes.

PRINCIPLE OF THE ASSAY

An anti-tag antibody is pre-coated onto the bottom of wells. After adding antigen or samples, Tagged-Capture antibody and HRP-conjugated detection antibody, a sandwich complex is formed in the solution. TMB acts as a HRP substrate, and the solution color will change from colorless to blue. A stop solution containing sulfuric acid turns the solution yellow. The color intensity is proportional to the quantity of bound protein, which is measurable at 450 nm with the correction wavelength set at 630 nm.

PRECISION

Intra-assay Precision (Precision within an assay) Three samples of known concentration were tested 8 times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in 16 separate assays to assess inter-assay precision.

Intra-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	8	2,525.7	58.9	2.3
2	8	622.6	20.3	3.3
3	8	297.4	10.5	3.5

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	16	2,539.4	57.5	2.3
2	16	628.3	20.3	3.2
3	16	308.8	20.3	6.6

RECOVERY

The recovery of mouse Cathepsin D spiked to three different levels throughout the range of the assay in mouse serum was evaluated.

Sample Type		Average% of Expected	Range (%)
Mouse serum	1:800	112	110-114
	1:1,600	98	84-107

LINEARITY

To assess the linearity of the assay, samples were diluted with the appropriate Sample Diluent to produce samples with values within the dynamic range of the assay. (The mouse serum was initially diluted 1:100.)

		Mouse serum
1:2	Average% of Expected	100
	Range (%)	-
1:4	Average% of Expected	91
	Range (%)	90-92
1:8	Average% of Expected	85
	Range (%)	84-86
1:16	Average% of Expected	85
	Range (%)	84-86

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant mouse Cathepsin D produced at Sunlong Medical™.

Ordering & shipping

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