Fluorogenic Peptidase Substrate with Cyclic Urea Spacer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current probes for detecting peptidase activity face challenges such as spontaneous degradation, false positive signals, and toxicity issues due to the use of certain spacers like aminobenzyl, which lead to enzyme inactivation and immune responses, limiting their sensitivity and biocompatibility.
Innovation Solution
Development of a peptidase substrate with a smart spacer that cyclizes into a cyclic urea, minimizing spontaneous degradation and enabling rapid fragmentation upon enzyme action, using diamine spacers pre-arranged for cyclization, which are biocompatible and do not cause permanent alkylation of proteins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aminobenzyl spacer is used in the probe, then the probe can detect peptidase activity, but the probe causes permanent alkylation of proteins and enzyme inactivation, leading to toxicity
Solution Approach 1:
The patent removes the harmful aminobenzyl spacer from the probe structure and replaces it with a diamine spacer that cyclizes to form a cyclic urea. This extraction of the harmful component eliminates protein alkylation and enzyme inactivation while preserving the detection function through the cyclic urea formation mechanism.
Solution Approach 2:
The patent converts the potentially harmful spontaneous hydrolysis issue into a beneficial feature by designing the diamine spacer to cyclize rapidly upon enzyme action. The cyclic urea formation is so rapid that it prevents spontaneous hydrolysis during storage, and the same cyclization mechanism that prevents harm also enables the detection signal.
2Ease of manufacture
If O,O acetal spacer is used, then the probe can be designed, but the probe undergoes spontaneous degradation producing false positive signals
Solution Approach 1:
The patent changes the chemical parameters of the spacer by using a diamine structure that forms a cyclic urea upon cyclization. This parameter change transforms the spacer from being prone to spontaneous degradation to being stable during storage, as the cyclic urea structure resists hydrolysis under physiological conditions.
Solution Approach 2:
The diamine spacer is pre-arranged to cyclize rapidly upon contact with the peptidase enzyme. This preliminary cyclization action occurs so quickly that it prevents any spontaneous degradation before detection can occur, ensuring that only enzyme-triggered signals are detected, not false positives from spontaneous hydrolysis.
3Measurement precision
If the probe operates in on/off mode with ESIPT fluorophore, then detection sensitivity is improved, but the fluorophore must be insoluble in aqueous media which complicates delivery
Solution Approach 1:
The patent segments the probe into two functional parts: a water-soluble peptide substrate portion that facilitates delivery and a hydrophobic ESIPT fluorophore portion that provides the detection signal. The diamine spacer acts as a bridge between these segments, allowing the hydrophobic fluorophore to be delivered to the enzyme while maintaining overall probe solubility through the peptide and spacer components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The substrate is stable, insensitive to spontaneous degradation, and provides a strong fluorescent signal upon peptidase action, operating in an off/on mode with high sensitivity and specificity, suitable for various applications including in vivo imaging without toxicity concerns.
Implementation Method 1
The substrate is stable, insensitive to spontaneous degradation, and provides a strong fluorescent signal upon peptidase action
Implementation Method 2
The class of fluorophores leading to intramolecular proton transfer in an excited state, called ESIPT (ESIPT from English 'Excited State Intramolecular Proton Transfer')
Implementation Method 3
The exceptional properties of ESIPT fluorophores are: (a) a large Stokes shift often exceeding 130 nm and capable of reaching values of 250 nm
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to novel peptidase substrates of formula (I): in which R0, R1, R2, R3, R4, R5 and n are as defined in claim 1, and to a method for detecting the presence of a catalytically active peptidase by means of one of these substrates.