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Today, 12 Ιουλίου 2016, 3:56:06 μμ
Lipid-based siRNA Delivery Systems: Challenges, Promises and Solutions Along the Long Journey
Today, 12 Ιουλίου 2016, 3:56:07 μμ
RNA interference (RNAi) is an evolutionary conserved highly specific gene-silencing mechanism initiated by small interfering RNA (siRNA) molecules. Fast-paced preclinical and clinical studies helped the siRNA technology become an efficient tool for undruggable targets in different diseases including genetic diseases, viral diseases and cancer. Despite great feature of siRNAs that can down-regulate any protein in the cells, the full potential and the success of the preclinical studies could not be translated into largely successful clinical outcomes. It has become clear that the possibility of overcoming the pitfalls for in vivo siRNA therapy fully depends on delivery systems. In this review, we start with the challenges and barriers for in vivo siRNA delivery. Then we briefly discuss the recent developments in siRNA modification technology. We specifically focused on siRNA lipidation and delivery approaches with special emphasis on the lipid based hybrid systems. Here we summarize the journey of lipid-based micelle-like nanoparticle systems that combine longevity in blood, effective cellular uptake and endosomal escape for successful siRNA delivery and discuss the multifunctional stimuli-sensitive systems based on lipids as the next generation smart systems.
Gender Differences in Autonomic Control of the Cardiovascular System
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Background: The autonomic nervous system (ANS) is a key regulator of the cardiovascular system. The two arms of the ANS, sympathetic and parasympathetic (vagal) have co-regulatory effects on cardiac homeostasis. ANS modulation and dysfunction are also believed to affect various cardiac disease states. Over the past decade, there has been increasing evidence suggesting gender differences in ANS activity. Methods: In multiple previous studies, ANS activity was primarily assessed using heart rate variability, muscle sympathetic nerve activity, coronary blood flow velocity, and plasma biomarkers. Heart rate variability is a non-invasive measure, which can be analyzed in terms of low frequency and high frequency oscillations, which indicate the sympathetic and parasympathetic tone, respectively. These measures have been studied between women and men in states of rest and stress, and in cardiac disease. Conclusion: Studies support the concept of a significant gender difference in ANS activity. Further studies are indicated to elucidate specific differences and mechanisms, which could guide targeted therapy of various cardiovascular disease states.
Polymer-Based Drug Delivery Systems, Development and Pre-Clinical Status
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Background: The nanomedicine is considered as the application of nanotechnology in the medical field where nanoparticles are sized in the nanoscale range. Drug delivery technologies are becoming increasingly important as a scientific area of investigation. Controlled-release systems and drug-targeting systems represents an alternative to traditional delivery nanoparticles, and the use of polymers is increasing nowadays. Although polymers could be classified as excipients, they are capable of modifying the biopharmaceutical and biokinetic behaviour of the transported active molecule increasing its efficacy and stability, and reduced cytotoxicity on healthy peripheral tissues. Methods: The goal of this work is to collect and analyse the most current polymeric nanoparticles development as controlledrelease and drug-targeting systems in cancer, infectious diseases and immunomodulation areas, as alternatives to conventional therapies. Results: This review provides an update on the polymeric nanoparticles development analysing the trend of polymeric-based drug delivery systems, future opportunities and challenges of this fast-growing area. Conclusion: With the thorough comprehension of biological effects depending on structure, it is possible to design specific systems for specific diseases, treatments and patients. The ability of polymer- based nanoparticles to modify and improve pharmacokinetics and pharmacodynamics, associated to techniques for enhancement of the therapeutic efficiency with minimal side effects, demonstrate the advantages of these systems.
Targeting the Cholinergic System for Neuroprotection and/or Enhancement of Functional Recovery Following Neurotrauma
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Development of novel pharmacotherapies for the treatment of traumatic injury to the nervous system has been ongoing for over 40 years. Despite many promising compounds discovered using animal models, no treatments have successfully translated into the clinic. The central dogma in this field is that brain trauma initiates a complex chain of biochemical events leading to secondary brain damage and sustained neurological deficits. The delayed secondary brain injury is likely to result from multiple insults including oxidative stress, mitochondrial dysfunction, breakdown of the blood brain barrier, dysregulated release of glutamate, pro-inflammatory cytokines, and other mediators. However, therapies targeting these systems have generally met with failure in clinical trials. The purpose of this review is to summarize the models used for preclinical neurotrauma research, provide a brief overview of previous failed clinical trials in head and spinal cord injury, and finally, to review involvement of the cholinergic system and discuss implications for future research. Possibilities and pitfalls of targeting the cholinergic system for neuroprotection and/or enhancement of functional recovery are also discussed.
The Melanocortin Receptor System: A Target for Multiple Degenerative Diseases
Today, 12 Ιουλίου 2016, 3:56:07 μμ
The melanocortin receptor system consists of five closely related G-protein coupled receptors (MC1R, MC2R, MC3R, MC4R and MC5R). These receptors are involved in many of the key biological functions for multicellular animals, including human beings. The natural agonist ligands for these receptors are derived by processing of a primordial animal gene product, proopiomelanocortin (POMC). The ligand for the MC2R is ACTH (Adrenal Corticotropic Hormone), a larger processed peptide from POMC. The natural ligands for the other 4 melanocortin receptors are smaller peptides including α-melanocyte stimulating hormone (α-MSH) and related peptides from POMC (β-MSH and γ-MSH). They all contain the sequence His-Phe-Arg-Trp that is conserved throughout evolution. Thus, there has been considerable difficulty in developing highly selective ligands for the MC1R, MC3R, MC4R and MC5R. In this brief review, we discuss the various approaches that have been taken to design agonist and antagonist analogues and derivatives of the POMC peptides that are selective for the MC1R, MC3R, MC4R and MC5R receptors, via peptide, nonpeptide and peptidomimetic derivatives and analogues and their differential interactions with receptors that may help account for these selectivities.
Thiophene Scaffold as Prospective Central Nervous System Agent: A Review
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Background: Heterocyclic compounds are extensively dispersed in nature and are vital for life. Various investigational approaches towards Structural Activity Relationship that focus upon the exploration of optimized candidates have become vastly important. </p><p> Method: Literature studies tell that for a series of compounds that are imperative in industrial and medicinal chemistry, thiophene acts as parent. Among various classes of heterocyclic compounds that have potential central nervous system activity, thiophene is the most important one. In the largely escalating chemical world of heterocyclic compounds showing potential pharmacological character, thiophene nucleus has been recognized as the budding entity. </p><p> Result: Seventeen Papers were included in this review article to define the central nervous system potential of thiophene. This review article enlightens the rationalized use and scope of thiophene scaffold as novel central nervous system activity such as anticonvulsant, acetylcholinesterase inhibitor, cyclin-dependent kinase 5 (cdk5/p25) inhibitors, CNS depressant, capability to block norepinephrine, serotonin and dopamine reuptake by their respective transporters etc. </p><p> Conclusion: The Finding of this review confirm the importance of thiophene scaffold as potential central nervous system agents. From this outcome, ideas for future molecular modifications leading to the novel derivatives with better constructive pharmacological potential may be derived. </p><p>
Is Nitric Oxide Assuming a Janus-Face in The Central Nervous System?
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Nitric Oxide, synthesized from L-arginine by the nitric oxide synthases, has a complex role within the human body. It contributes to almost every physiological system and has been found to be both protective and toxic in disease states. An aging population faces an increasing incidence of neurodegenerative disease and the pathological action of nitric oxide in Alzheimer’s and Parkinson’s diseases may be important therapeutic targets for the future. Nitric oxide’s protective effects are also important to consider, through inhibition of caspase-3, nitrosylation of NMDA and increased activation of protein kinase B and CREB transcription factor. Nitric oxide has been shown to play a part in long term potentiation, revealing its importance in synaptic plasticity. Due to nitric oxide’s mixed effects it is an exciting and varied therapeutic target. Currently, the impact of these therapies has been explored and developed in animal studies, but is yet to be fully realized in human trials. This paper outlines both the pathological and protective roles of nitric oxide in the central nervous system and the potential pharmacological therapies and targets these indicate.
Hypoxia Responsive Drug Delivery Systems in Tumor Therapy
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Hypoxia is a common characteristic of solid tumors. It is mainly determined by low levels of oxygen resulting from imperfect vascular networks supplying most tumors. In an attempt to improve the present chemotherapeutic treatment and reduce associated side effects, several prodrug strategies have been introduced to achieve hypoxia-specific delivery of cytotoxic anticancer agents. With the advances in nanotechnology, novel delivery systems activated by the consequent outcomes of hypoxia have been developed. However, developing hypoxia responsive drug delivery systems (which only depend on low oxygen levels) is currently naïve. </p> <p> This review discusses four main hypoxia responsive delivery systems: polymeric based drug delivery systems, oxygen delivery systems combined with radiotherapy and chemotherapy, anaerobic bacteria which are used for delivery of genes to express anticancer proteins such as tumor necrosis alpha (TNF-α) and hypoxia-inducible transcription factors 1 alpha (HIF1α) responsive gene delivery systems.
Correlation between Systemic Lupus Erythematosus Activity and Plasma Levels of Monomeric Prolactin and Macroprolactin
Today, 12 Ιουλίου 2016, 3:56:07 μμ
The correlation of prolactin (PRL) levels with SLE activity is a controversial issue, which could be explained by the presence of macroprolactin (MPRL), a high molecular weight form of PRL with a lower in vivo biological activity. </p><p> Objectives: We aimed to evaluate the prevalence of hyperprolactinemia, PRL and MPRL levels in SLE patients, and to correlate these levels with disease activity as measured by the SLE Disease Activity Index (SLEDAI). </p><p> Material and Methods: We conducted a case-control, cross-sectional study with 73 SLE patients (L group), sixty-two of which were evaluated before and after treatment, and correlated the results with serum PRL and MPRL levels. These results were compared to those of 29 healthy women with ovulatory cycles (C group) and 34 women in the third trimester of pregnancy (G group). </p><p> Results: Mean PRL levels were: 8,8 ng/ml on C group; 12,0 ng/ml on L group (p = 0.02) and 158,5 ng/ml on G group. Hyperprolactinemia was present in 19.4% of SLE patients, but was not found on C group. The MPRL form was predominant among 20.5% of SLE patients, in none of the C group and in only 5.8% of pregnant women. There was a strong correlation between the PRL levels and SLE activity, regardless of the hormone’s molecular form. SLE treatment was able to reduce levels of all forms of PRL. The predominance of MPRL, however, did not change after treatment. </p><p> Conclusions: Despite its lower biological activity, MPRL levels correlated with LES activity as much as free prolactin. </p><p>
Tet-On Systems For Doxycycline-inducible Gene Expression
Today, 12 Ιουλίου 2016, 3:56:07 μμ
The tetracycline-controlled Tet-Off and Tet-On gene expression systems are used to regulate the activity of genes in eukaryotic cells in diverse settings, varying from basic biological research to biotechnology and gene therapy applications. These systems are based on regulatory elements that control the activity of the tetracycline-resistance operon in bacteria. The Tet-Off system allows silencing of gene expression by administration of tetracycline (Tc) or tetracycline-derivatives like doxycycline (dox), whereas the Tet-On system allows activation of gene expression by dox. Since the initial design and construction of the original Tet-system, these bacterium-derived systems have been significantly improved for their function in eukaryotic cells. We here review how a dox-controlled HIV-1 variant was designed and used to greatly improve the activity and dox-sensitivity of the rtTA transcriptional activator component of the Tet-On system. These optimized rtTA variants require less dox for activation, which will reduce side effects and allow gene control in tissues where a relatively low dox level can be reached, such as the brain.
Design and Development of Nanoemulsion Systems Containing Interferon Gamma
Today, 12 Ιουλίου 2016, 3:56:07 μμ
The aim of this study was to design and develop stable nanoemulsion formulations containing IFN-γ to probe their use as an immunomodulating agent. The nanoemulsions comprising distilled water, triglycerides of capric acid/caprylic, sobitan-oleate (SP), polysorbate 80 (TW) and propylene glycol (PG) were prepared through ultra-homogenization and characterized regarding droplet size, polydispersity, surface charge, preliminary and accelerated physical stability, and rheological properties. Stable nanoemulsions were selected to incorporate nano doses of IFN-γ (100 ng.mL<sup>-1</sup>). The influence of IFN-γ incorporated nanoemulsions on functional activity of mononuclear cell for Escherichia coli enteropathogenic was analyzed through superoxide release, phagocytosis, microbicidal activity and intracellular calcium release. The optimized formulation, comprising aqueous and oily phase of 10 % and 80 %, respectively, and surfactant mix ratio (SP/TW/PG) of 3.5/5.5/1.0, remained stable in extreme conditions during 90 days, displaying oil-in-water characteristics, biocompatible pH value, significant maintenance of its rheological profile, hydrodynamic radius of 205 nm, zeta potential of -40 mV and average dose of IFN-γ 91 ng.mL<sup>-1</sup>. The developed formulation did not alter the MN cell viability rates. Increased the superoxide release, phagocytosis index and intracellular calcium release of MN cells of human blood. Our findings indicate that the produced formulation improved the immunomodulatory activity of the IFN-γ.
Recent Progress in Dendrimer-based Gene Delivery Systems
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Due to core-shell nanostructures, highly branched and star-shaped macromolecules with three dimensional structural symmetry, dendrimers have been widely used as non-viral vectors in gene delivery. However, the performance of dendrimer-based gene vectors is far from ideal, mainly because of the low transfection efficiency and serious cytotoxicity. Therefore, many researchers focused on how to improve the transfection efficiency and reduce the cytotoxicity in the past decade. In this review, we mainly reported the most recent advances of dendrimer-based gene delivery systems. Several typical types of dendrimers for gene delivery were reviewed in detail, such as poly (amido amine) (PAMAM), poly (propylene imine) (PPI), poly(ether imine), poly-Llysine dendrimers. Recent advances about other types of dendrimer were also briefly mentioned. These advances provide a promising route to improve the transfection efficiency and reduce the toxicity, which also illustrates the direction of the future development of dendrimers in gene delivery.
Advances in Sub-Micron Particle Based Aerosol Strategies for Efficient Systemic Delivery of Therapeutic Agents
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Background: Over the past few decades, the field of nanotechnology has led to significant advances in healthcare, impacting both diagnosis and therapy. Systemic delivery of therapeutics via inhalation route has also advanced with the use of sub micron particles as colloidal drug carriers. Use of inhalable nanocarriers for delivering drugs systemically offers additional degree of control and manipulation, thereby maximizing the alveolar deposition and minimizing clearance. The ramifications are improved systemic absorption and higher therapeutic efficacy. Herein, we review the progress and advances related to nanoparticle based inhalable formulations for systemic delivery of therapeutics, and also discusses the associated challenges. Methods: We performed detailed searches in PubMed and compiled the literature on inhalable nanoparticles for systemic delivery of therapeutic agents. Results: To date, multiple inhalable nanocarriers have been explored for systemic delivery of therapeutics; and can be broadly classified into three categories, viz. lipid based nanoparticles, polymeric nanoparticles and porous nanoparticle aggregate particles. Conclusion: In spite of the promising data, there are still multiple challenges, including poor understanding of nanotoxicology of therapeutic nanoparticles. Overcoming these challenges can lead to successful clinical translation of inhalable nanoparticles for systemic drug delivery, leading to the development of more effective and patient compliant therapies.
Systemic Application of Anti-inflammatory Agents in Periodontal Treatment
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Periodontitis is a group of inflammatory diseases with infectious etiology characterized by destruction of tooth supporting tissues. Periodontal treatment aims to suppress periodontal pathogens mainly through mechanical debridement. Anti-inflammatory drugs, especially non-steroidal antiinflammatory drugs (NSAIDs), have been proposed as adjunctive therapy. This review aims to provide an overview on the potential effects of systemic use of NSAIDs on periodontal treatment outcomes. Several NSAIDs, non-selective and selective COX inhibitors have been evaluated. Some of them improve clinical outcomes of mechanical periodontal treatment and, in some cases, also induce changes in the biochemical profile of gingival crevicular fluid. However, the results obtained should be balanced with the potential side effects of these drugs.
Janus Nano- and Microparticles as Smart Drug Delivery Systems
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Research has been lately prospering in the field of Janus nanoparticles, focusing on new synthesis techniques and their application in various fields. This is due to the unique characteristics possessed by this type of particles such as their anisotropic nature, and their synergistic potential for combination therapy in addition to the multilevel targeting. These unique features are essential in several biomedical applications, especially the controlled drug delivery. Various techniques have been used for the synthesis of Janus nanoparticles including; masking, self-assembly, microfluidic and phase separation. They are all aiming at production of uniformly sized Janus particles with spatially separated functionalities. Herein, the main synthesis approaches of various Janus nanoparticles are briefly reviewed with the provision of examples of studies focusing on the potential applications of Janus particles in controlled drug delivery.
Serotonergic Drugs: Agonists/Antagonists at Specific Serotonergic Subreceptors for the Treatment of Cognitive, Depressant and Psychotic Symptoms in Alzheimer’s Disease
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Background: Alzheimer’s disease is a neurodegenerative disease showing alterations in classical neurotransmitters, above all in the hippocampus and prefrontal/temporal cortices. In this disease, acetylcholine shows hypoactivity, noradrenaline first shows hyperactivity, and during the course of the disease an increasing hypoactivity, glutamate shows hyperactivity and excitotoxicity and GABA shows hypoactivity. In post-mortem studies, serotonin levels and the number of specific serotonergic subreceptors, for example 5-HT<sub>1B</sub> receptors, decreased. Methods: We summarized the alterations of classical neurotransmitters in the brain regions involved in cognitive, depressive and psychotic symptoms in Alzheimer’s disease. Starting from these neurotransmitter alterations, we describe neural networks including specific serotonergic subreceptors in the involved brain regions. Results: In the hippocampus and prefrontal cortex, serotonin levels are associated with cognitive functions, whereas in the brainstem serotonin levels are related with affective symptoms. Psychotic symptoms which can occur in patients with Alzheimer’s disease are associated with dopamine and serotonin hyperactivity in the mesolimbic system and hippocampus. The interaction between classical neurotransmitters and their specific subreceptors is shown in different brain areas. Conclusion: In clinical trials, the therapeutic effects of 5-HT<sub>4</sub>, 5-HT<sub>7</sub> agonists and 5-HT<sub>3</sub>, 5-HT<sub>6</sub> antagonists have been examined to improve cognitive symptoms in Alzheimer’s disease. In these trials, 5-HT<sub>4</sub> agonists and 5-HT<sub>4</sub> antagonists showed a significant better effect in improving cognitive functions than placebo. The effect of such drugs on the formation of amyloid plaques is also examined. The appropriate use of antidepressant and antipsychotic drugs with an agonism or antagonism at specific serotonergic subreceptors is pointed out. Serotonin-selective antidepressant drugs significantly improve depressant symptoms and daily activities in Alzheimer patients and they are used to treat aggressive behaviour. Among the second-generations antipsychotic drugs (D<sub>2</sub> and 5-HT<sub>2A</sub> antagonists), drugs with a favorable metabolic profile should be used.
Screening of Potential Anticancer Compounds from Sargassum wightii to Target Breast Cancer Specific HER2 Receptor using in-silico Analysis
Today, 12 Ιουλίου 2016, 3:56:07 μμ
The present research focuses on the molecular docking analysis of the isolated compound from the seaweed “Sargassum wightii” on cancer specific HER2 or HER2/neu also known as CD340. The ethanol derived compounds capable of binding to HER2 receptor is implicated for the breast cancer. The crystal structure of the HER2 protein with the resolution of 1.63Ao (Pdb entry 4RJ3) collected from the pdb website (www.pdb). Missing alignments and the side chains are prepared to fit for the insilico analysis. Seven bioactive compounds isolated from the hydro-alcoholic mixture using GC-MS are docked against HER2 using Schrodinger 2013.1 (Glide version 5.9). The binding sites, glide score and the energy of the 7 compounds with the HER2 protein are compared. The isolated compounds with most negative glide score such as benzoic acid, 2-hydroxy-ethyl ester, methyl salicylate, diethyl phthalate and phytol exhibited efficient in inhibiting the HER2 receptor of breast cancer. The Pharmacokinetics and Pharmacodynamics (ADME) properties of the selected highest glide scored compounds are performed using QikProp 3.6 module from Schrodinger-Maestro software. The compounds were showed significant ADME properties in basic criteria of Molecular weight (MW), H-Bond donor, H-Bond acceptor and log P (O/W). The results of the study showed that the compounds of “Sargassum wightii” may be a good target for breast Cancer.
Electrocardiographic and Cardiac Autonomic Indices - Implications of Sex-Specific Risk Stratification in Women After Acute Myocardial Infarction
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Background: The debate on whether sex-specific predictive models improve risk stratification after myocardial infarction is ongoing. Methods: This review summarises the current clinical knowledge on sex-specific differences in post-infarction risk stratification parameters. Particular focus is given to electrocardiographic risk factors and indices of cardiac autonomic status. Results: Differences in the underlying pathophysiology between men and women are known. However, clinical findings often lead to uncertain conclusions for a number of risk predictors including, among others, resting heart rate, heart rate variability, heart rate turbulence, QT interval duration, and QRS-T angle. The review links recent findings in prognostic parameters with successful approaches in sex-specific non-invasive risk stratification. Conclusion: Disparities are described in the current clinical opinions on the relevance of investigated parameters in women and possible directions for further research in the field are given.
Cardiac Specific Overexpression of hHole Attenuates Isoproterenol–Induced Hypertrophic Remodeling through Inhibition of Extracellular Signal-Regulated Kinases (ERKs) Signalling
Today, 12 Ιουλίου 2016, 3:56:07 μμ
The human Hole gene (hHole) encodes a six-transmembrane protein with 319- amino acids. Our previous study showed that hHole was strongly expressed in adult heart and may act as a suppressor of extracellular signal-regulated kinases (ERKs), overactivation of which contributed to pathological cardiac hypertrophy. In this study, it was observed that Hole expression was up-regulated in murine hypertrophic hearts. In a cardiac specific transgenic mouse model, it was observed that overexpression of hHole specifically in heart attenuated cardiac hypertrophy and fibrosis induced by isoproterenol (ISO), with blunted transcriptions of ERK1/2, total ERK1/2 proteins and phosphorylated ERK1/2 (p-ERK1/2) levels. Furthermore, overexpression of hHole in mice by hydrodynamic tail-vein injection with hHole plamids also inhibited cardiac hypertrophy induced by ISO. Our work identified hHole as a novel repressor of cardiac hypertrophy, and provided new insights into the possible target for the prevention or treatment of cardiac diseases.
Importance of Amino Acids, Gln-119 and Tyr-376, in the S1 Pocket of Escherichia coli Peptidase N in Determining Substrate Specificity
Today, 12 Ιουλίου 2016, 3:56:07 μμ
Peptidase N (PepN) is a broad specific metallo-peptidase and the sole member of the M1 class encoded by Escherichia coli. Comparative analysis of residues present in the S1 subsite of E. coli PepN with other family members revealed that Tyr-381 is conserved whereas Glu-121, Gln-119 and Tyr-376 are partially conserved. The functional importance of these amino acids was investigated by protein engineering studies. The change in Glu-121 to Gln and Tyr-381 to Phe led to catalytically inactive PepN. At the same time, the change in Gln-119 to His (Q119H) and Tyr-376 to Phe (Y376F) led to alterations in substrate specificity. Kinetic studies revealed that purified PepN variants, Q119H and Y376F, cleaved some substrates (e.g. Arg) similar to wild type PepN. However, these variants displayed lower efficacy with other substrates (e.g. Tyr, AAF and Suc-AAF). Q119H or Y376F, cleave a natural peptide (insulin B chain) and a loosely folded protein (casein) with greatly reduced efficacy. The double mutant, i.e. harboring both Q119H and Y376F, displays greatly reduced catalytic activity with respect to all substrates studied. The in vivo significance was addressed by expressing these variants in ΔpepN during nutritional downshift and high temperature (NDHT) stress. Compared to wild type PepN, the Y376F and Q119H variants display lower intracellular amounts of free N-terminal amino acids and reduction in growth during NDHT stress. Finally, structural modeling, using the crystal structure of E. coli PepN bound to substrates, Arg or Tyr, shed insights into the roles of Q119H and Y376F in determining substrate preferences.
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