Severity: Warning
Message: file_get_contents(https://...@gmail.com&api_key=61f08fa0b96a73de8c900d749fcb997acc09): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 143
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 143
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 209
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3098
Function: getPubMedXML
File: /var/www/html/application/controllers/Detail.php
Line: 574
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 488
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Severity: Warning
Message: Attempt to read property "Count" on bool
Filename: helpers/my_audit_helper.php
Line Number: 3100
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3100
Function: _error_handler
File: /var/www/html/application/controllers/Detail.php
Line: 574
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 488
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Receptor-derived peptides have played an important role in elucidating chemokine-receptor interactions. For the inflammatory chemokine CXC-class chemokine ligand 8 (CXCL8), a site II-mimetic peptide has been derived from parts of extracellular loops 2 and 3 and adjacent transmembrane helices of its receptor CXC-class chemokine receptor 1 (Helmer et al., RSC Adv., 2015, 5, 25657). The peptide sequence with a C-terminal glutamine did not bind to CXCL8, whereas one with a C-terminal glutamate did but with low micromolar affinity. We sought to improve the affinity and protease stability of the latter peptide through cyclization while also cyclizing the former for control purposes. To identify a cyclization strategy that permits a receptor-like interaction, we conducted a molecular dynamics simulation of CXCL8 in complex with full-length CXC-class chemokine receptor 1. We introduced a linker to provide an appropriate spacing between the termini and used an on-resin side-chain-to-tail cyclization strategy. Upon chemokine binding, the fluorescence intensity of the tetramethylrhodamine (TAMRA)-labeled cyclic peptides increased whereas the fluorescence anisotropy decreased. Additional molecular dynamics simulations indicated that the fluorophore interacts with the peptide macrocycle so that chemokine binding leads to its displacement and observed changes in fluorescence. Macrocyclization of both 18-amino acid-long peptides led to the same low micromolar affinity for CXCL8. Likewise, both TAMRA-labeled linear peptides interacted with CXCL8 with similar affinities. Interestingly, the linear TAMRA-labeled peptides were more resistant to tryptic digestion than the unlabeled counterparts, whereas the cyclized peptides were not degraded at all. We conclude that the TAMRA fluorophore tends to interact with peptides altering their protease stability and behavior in fluorescence-based assays.
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Source |
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http://dx.doi.org/10.1002/psc.3486 | DOI Listing |
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