Site-specific N-terminus conjugation of poly(mPEG1100) methacrylates to salmon calcitonin: synthesis and preliminary biological evaluation

As described elsewhere in this Special Issue on biomarkers, much progress has been made in the detection of modified DNA within organisms at endogenous and exogenous levels of exposure to chemical species, including putative carcinogens and chemotherapeutic agents. Advances in the detection of damaged or unnatural bases have been able to provide correlations to support or refute hypotheses between the level of exposure to oxidative, alkylative, and other stresses, and the resulting DNA damage (lesion formation). However, such stresses can form a plethora of modified nucleobases, and it is therefore difficult to determine the individual contribution of a particular modification to alter a cell’s genetic fate, as measured in the form of toxicity by stalled replication past the damage, by subsequent mutation, and by lesion repair. Chemical incorporation of a modification at a specific site within a vector (site-specific mutagenesis) has been a useful tool to deconvolute what types of damage quantified in biologically relevant systems may lead to toxicity and/or mutagenicity, thereby allowing researchers to focus on the most relevant biomarkers that may impact human health. Here, we will review a sampling of the DNA modifications that have been studied by shuttle vector techniques.

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Tau Is Truncated in Five Regions of the Normal Adult Human Brain

International Journal of Molecular Sciences ◽

10.3390/ijms22073521 ◽

2021 ◽

Vol 22 (7) ◽

pp. 3521

Author(s):

Michael G. Friedrich ◽

Amanda Skora ◽

Sarah E. Hancock ◽

Todd W. Mitchell ◽

Paul L. Else ◽

...

Keyword(s):

Prefrontal Cortex ◽

Human Brain ◽

Normal Subjects ◽

Brain Regions ◽

Brain Cells ◽

Site Specific ◽

N Terminus ◽

Normal Human ◽

Age Range ◽

Tau Cleavage

The truncation of Tau is thought to be important in promoting aggregation, with this feature characterising the pathology of dementias such as Alzheimer disease. Antibodies to the C-terminal and N-terminal regions of Tau were employed to examine Tau cleavage in five human brain regions: the entorhinal cortex, prefrontal cortex, motor cortex, hippocampus, and cerebellum. These were obtained from normal subjects ranging in age from 18 to 104 years. Tau fragments of approximately 40 kDa and 45 kDa with an intact N-terminus retained were found in soluble and insoluble brain fractions. In addition, smaller C-terminal Tau fragments ranging in mass from 17 kDa to 25 kDa were also detected. These findings are consistent with significant Tau cleavage taking place in brain regions from 18 years onwards. It appears that site-specific cleavage of Tau is widespread in the normal human brain, and that large Tau fragments that contain the N-terminus, as well as shorter C-terminal Tau fragments, are present in brain cells across the age range.

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Exploiting Protein N-Terminus for Site-Specific Bioconjugation

Molecules ◽

10.3390/molecules26123521 ◽

2021 ◽

Vol 26 (12) ◽

pp. 3521

Author(s):

Lucia De Rosa ◽

Rossella Di Stasi ◽

Alessandra Romanelli ◽

Luca Domenico D’Andrea

Keyword(s):

Protein Molecule ◽

Amine Group ◽

Reactive Site ◽

Reaction Conditions ◽

Selective Labeling ◽

Site Specific ◽

Protein Conjugates ◽

Protein Molecules ◽

N Terminus

Although a plethora of chemistries have been developed to selectively decorate protein molecules, novel strategies continue to be reported with the final aim of improving selectivity and mildness of the reaction conditions, preserve protein integrity, and fulfill all the increasing requirements of the modern applications of protein conjugates. The targeting of the protein N-terminal alpha-amine group appears a convenient solution to the issue, emerging as a useful and unique reactive site universally present in each protein molecule. Herein, we provide an updated overview of the methodologies developed until today to afford the selective modification of proteins through the targeting of the N-terminal alpha-amine. Chemical and enzymatic strategies enabling the selective labeling of the protein N-terminal alpha-amine group are described.

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