Other Biochemistry, Biophysics, and Structural Biology Commons^™

Analyzing Functional Interactions Of Designed Peptides By Nmr Spectroscopy, Wonsuk Choi

Pharmaceutical Sciences (MS) Theses

The development of small peptide-based therapeutics can be accelerated by the knowledge of relationships between the peptide structure and its functional interactions. Here, we report the analysis of two groups of synthetic peptides designed for two applications – broad bactericidal action and inhibition of protein-protein interactions in human cells. Novel amphiphilic peptides designed for antibacterial application incorporated arginine as cationic amino acids and non-natural amino acids that have aromatic side chains with similar hydrophobic properties as tryptophan. The interaction of lead cyclic peptides and their linear analogs with a phospholipid bilayer mimicking a bacterial membrane was studied using nuclear magnetic …

Nanodiscs: A Novel Approach To The Study Of The Methionine Abc Transporter System, Michael T. Winslow

Master's Theses

Membrane transporter proteins play the vital role of moving compounds in and out of the cell and are essential for all living organisms. ATP Binding Cassette (ABC) family transporters function both as importers and exporters in prokaryotes. MetNI is an E. coli Type I ABC transporter responsible for the uptake of methionine into the cytosol from the cell periplasmic space through the cell membrane to maintain intracellular methionine pools. ABC transporters, like other membrane proteins, are most often mechanistically and structurally studied in vitro, solubilized by detergents. However, detergent micelles may affect the conformational changes of membrane proteins relative to …

Role Of Fat Content On The Structure And Function Of Human Skeletal Muscle, Joseph A. Gordon Iii

Doctoral Dissertations

Muscle size does not fully explain variations in muscle strength. Fat content has been implicated in muscle weakness, though this relationship remains unclear. The relationship between fat and strength may vary between scales (e.g., cellular, organ, and organism). The goal of this dissertation was to clarify the role of fat in the structure and function of muscle using in vitro and in vivo techniques across multiple scales in adults 21-45 years old. Study 1 tested the agreement of intramyocellular lipid (IMCL) content between oil red o (ORO) and magnetic resonance spectroscopy (MRS) techniques. These measures of IMCL were also compared …

Du Undergraduate Showcase: Research, Scholarship, And Creative Works, Caitlyn Aldersea, Justin Bravo, Sam Allen, Anna Block, Connor Block, Emma Buechler, Maria De Los Angeles Bustillos, Arianna Carlson, William Christensen, Olivia Kachulis, Noah Craver, Kate Dillon, Muskan Fatima, Angel Fernandes, Emma Finch, Colleen Cassidy, Amy Fishman, Andrea Francis, Stacia Fritz, Simran Gill, Emma Gries, Rylie Hansen, Shannon Powers, Jacqueline Martinez, Zachary Harker, Ashley Hasty, Mykaela Tanino-Springsteen, Kathleen Hopps, Adelaide Kerenick, Colin Kleckner, Ci Koehring, Elijah Kruger, Braden Krumholz, Maddie Leake, Lyneé Alves, Seraphina Loukas, Yatzari Lozano Vazquez, Haley Maki, Emily Martinez, Sierra Mckinney, Mykaela Tanino-Springsteen, Audrey Mitchell, Kipling Newman, Audrey Ng, Megan Lucyshyn, Andrew Nguyen, Stevie Ostman, Casandra Pearson, Alexandra Penney, Julia Gielczynski, Tyler Ball, Anna Rini, Christina Rorres, Simon Ruland, Helayna Schafer, Emma Sellers, Sarah Schuller, Claire Shaver, Kevin Summers, Isabella Shaw, Madison Sinar, Claudia Pena, Apshara Siwakoti, Carter Sorensen, Madi Sousa, Anna Sparling, Alexandra Revier, Brandon Thierry, Dylan Tyree, Maggie Williams, Lauren Wols

DU Undergraduate Research Journal Archive

DU Undergraduate Showcase: Research, Scholarship, and Creative Works

Therapies For Mitochondrial Disorders, Kayli Sousa Smyth, Anne Mulvihill

SURE Journal: Science Undergraduate Research Experience Journal

Mitochondria are cytoplasmic, double-membrane organelles that synthesise adenosine triphosphate (ATP). Mitochondria contain their own genome, mitochondrial DNA (mtDNA), which is maternally inherited from the oocyte. Mitochondrial proteins are encoded by either nuclear DNA (nDNA) or mtDNA, and both code for proteins forming the mitochondrial oxidative phosphorylation (OXPHOS) complexes of the respiratory chain. These complexes form a chain that allows the passage of electrons down the electron transport chain (ETC) through a proton motive force, creating ATP from adenosine diphosphate (ADP). This study aims to explore current and prospective therapies for mitochondrial disorders (MTDS). MTDS are clinical syndromes coupled with abnormalities …

Arginine Methylation Of The Pgc-1Α C‑Terminus Is Temperature- Dependent, Meryl Mendoz, Mariel Mendoza, Tiffany Lubrino, Sidney Briski, Immaculeta Osuji, Janielle Cuala, Brendan Ly, Ivan Ocegueda, Harvey Peralta, Benjamin A. Garcia, Cecilia Zurita-Lopez

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

We set out to determine whether the C-terminus (amino acids 481–798) of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α, UniProt Q9UBK2), a regulatory metabolic protein involved in mitochondrial biogenesis, and respiration, is an arginine methyltransferase substrate. Arginine methylation by protein arginine methyltransferases (PRMTs) alters protein function and thus contributes to various cellular processes. In addition to confirming methylation of the C-terminus by PRMT1 as described in the literature, we have identified methylation by another member of the PRMT family, PRMT7. We performed in vitro methylation reactions using recombinant mammalian PRMT7 and PRMT1 at 37, 30, 21, 18, and 4 °C. …

Hyper Stable Variants Of Fgf-1-Fgf-2 Dimer, Madison Shields Mcclanahan

Chemistry & Biochemistry Undergraduate Honors Theses

Fibroblast Growth Factors (FGFs), including FGF-1 and FGF-2, are proteins that play a crucial role in cell proliferation, cell differentiation, cell migration, and tissue repair. FGF-1 and FGF-2 are useful in accelerating the healing process in the human body; however, these proteins are naturally thermally unstable, resulting in a relatively low half-life in vivo. 1,8 In efforts to improve the stability of this protein, FGF-1 and FGF-2 proteins are engineered by combining the amino acid sequences of the two proteins to form a heterodimer and obtain novel properties. These two FGF variants are chosen for their specific wound healing capabilities. …

Modulation Of Kras Structure And Dynamics By Kras Ubiquitination And Membrane Depolarization, Vinay Nair

Dissertations & Theses (Open Access)

KRAS, a 21 kDa small GTPase protein, functions as a molecular switch playing a key role in regulating cell proliferation. Dysregulation of KRAS signaling by oncogenic mutations leads to uncontrolled cell proliferation, a hallmark of cancer cells. Attempts to therapeutically target oncogenic KRAS have led to limited success resulting in a need to identify new mechanisms to targeting KRAS. The interaction of KRAS with its regulators, effectors, and the membrane present one such avenue. In this study, we investigated how post-translational covalent and environmental modifications could modulate these interactions of KRAS. Using computational molecular dynamics simulations, nuclear magnetic resonance spectroscopy …

The Development Of Inhibitors For Sars-Cov-2 Orf8, My Thanh Thao Nguyen

CSB and SJU Distinguished Thesis

An unexpected outbreak of SARS-CoV-2 caused a worldwide pandemic in 2020. Many repurposed drugs were tested, but there are currently only three FDA approved antivirals (Merck’s antiviral Molnupiravir, Pfizer’s antiviral Paxlovid, and Remdisivir).1 Most of the antiviral drugs tested SARS-CoV-2 main protease and RNA-dependent RNA polymerase. However, it is important to explore different drug targets of SARS-CoV-2 to prepare for the virus mutations of the future. This research looks at an alternative approach in which SARSCoV- 2 Open Reading Frame 8 (ORF8), which has been shown to be a rapidly evolving hypervariable gene, was chosen to be the protein of …

Sars-Cov-2 Main Protease Inhibitors Repurposed For Hiv-1 Protease Binding, Jacob Minkkinen

CSB and SJU Distinguished Thesis

Severe acute respiratory syndrome (SARS-CoV-2) led to the COVID-19 global pandemic, with over 460 million cases of infection and over 6 million deaths since the start of the pandemic. SARS-CoV-2 is a retrovirus that utilizes a main protease (Mpro). Mpro is a catalytic cys/his protease. Several treatments were proposed to stop the pandemic including repurposing drugs to inhibit the Mpro. Another retrovirus that uses a protease is human immunodeficiency virus (HIV-1) which has been a global epidemic for 40 years and is a devastating disease that attacks the immune system. HIV-1 has infected 79.5 million people and has killed an …

Conformational Flexibility And Local Frustration In The Functional States Of The Sars-Cov-2 Spike B.1.1.7 And B.1.351 Variants: Mutation-Induced Allosteric Modulation Mechanism Of Functional Dynamics And Protein Stability, Gennady M. Verkhivker

Mathematics, Physics, and Computer Science Faculty Articles and Research

Structural and functional studies of the SARS-CoV-2 spike proteins have recently determined distinct functional states of the B.1.1.7 and B.1.351 spike variants, providing a molecular framework for understanding the mechanisms that link the effect of mutations with the enhanced virus infectivity and transmissibility. A detailed dynamic and energetic analysis of these variants was undertaken in the present work to quantify the effects of different mutations on functional conformational changes and stability of the SARS-CoV-2 spike protein. We employed the efficient and accurate coarse-grained (CG) simulations of multiple functional states of the D614G mutant, B.1.1.7 and B.1.351 spike variants to characterize …

Analysis Of The Antimicrobial Activity Of The Novel Chemotherapeutic Drug, Tpp1, Against Pseudomonas Aeruginosa And The Hydrogel Delivery Of Water-Soluble Antimicrobial Compounds, Alex Gasper

Senior Independent Study Theses

Cancer is one of the leading causes of death in the world, and it is commonly linked with bacterial infections that often complicate treatments. Recently, chemotherapeutics have been developed that are able to act as anti-cancer agents using delocalized lipophilic cations (DLCs) that are able to specifically target mitochondrial membranes of cancer cells. TPP1 is a newly developed chemotherapeutic drug that has activity against bladder cancer and melanoma cell lines in vitro. In order to determine if TPP1 has antimicrobial activity, TPP1 was tested against a common bacteria, Pseudomonas aeruginosa, to determine if antimicrobial activity was present. This testing was …

Physiological Roles Of Mammalian Transmembrane Adenylyl Cyclase Isoforms, Katrina F. Ostrom, Justin E. Lavigne, Tarsis F. Brust, Roland Seifert, Carmen Dessauer, Val J. Watts, Rennolds S. Ostrom

Pharmacy Faculty Articles and Research

Adenylyl cyclases (ACs) catalyze the conversion of ATP to the ubiquitous second messenger cAMP. Mammals possess nine isoforms of transmembrane ACs, dubbed AC1-9, that serve as major effector enzymes of G protein-coupled receptors. The transmembrane ACs display varying expression patterns across tissues, giving potential for them having a wide array of physiologic roles. Cells express multiple AC isoforms, implying that ACs have redundant functions. Furthermore, all transmembrane ACs are activated by Gα_s so it was long assumed that all ACs are activated by Gα_s-coupled GPCRs. AC isoforms partition to different microdomains of the plasma membrane and form …

The Structural And Functional Role Of Photosensing In Rgs-Lov Proteins, Zaynab Jaber

Dissertations, Theses, and Capstone Projects

Light provides organisms with energy and spatiotemporal information. To survive and adapt, organisms have developed the ability to sense light to drive biochemical effects that underlie vision, entrainment of circadian rhythm, stress response, virulence, and many other important molecularly driven responses. Blue-light sensing Light-Oxygen-Voltage (LOV) domains are ubiquitous across multiple kingdoms of life and modulate various physiological events via diverse effector domains. Using a small molecule flavin chromophore, the LOV domain undergoes light-dependent structural changes leading to activation or repression of these catalytic and non-catalytic effectors. In silico analyses of high-throughput genomic sequencing data has led to the marked expansion …

Covid19 Disease Map, A Computational Knowledge Repository Of Virus–Host Interaction Mechanisms, Marek Ostaszewski, Tomáš Helikar, Bhanwar Lal Puniya, A Host Of Co-Authors, Covid-19 Disease Map Community

Department of Biochemistry: Faculty Publications

We need to effectively combine the knowledge from surging literature with complex datasets to propose mechanistic models of SARS-CoV-2 infection, improving data interpretation and predicting key targets of intervention. Here, we describe a large-scale community effort to build an open access, interoperable and computable repository of COVID-19 molecular mechanisms. The COVID-19 Disease Map (C19DMap) is a graphical, interactive representation of disease-relevant molecular mechanisms linking many knowledge sources. Notably, it is a computational resource for graph-based analyses and disease modelling. To this end, we established a framework of tools, platforms and guidelines necessary for a multifaceted community of biocurators, domain experts, …

Open Neuroscience Initiative, Austin Lim

College of Science and Health Full Text Publications

The Open Neuroscience Initiative is a free-to-use textbook

This project began as a means to overcoming the financial burden that face undergraduate neuroscience students when buying textbooks. By compiling and writing a completely free-to-access textbook that covers the foundations of a typical college introduction to neuroscience course, students would have one less obstacle to overcome in their educational career, allowing them to focus their valuable time and attention on learning rather than finances. To make this project a reality, I began with a humble tweet in May 2019 that managed to gain a tiny bit of traction among the neuroscience …

Modulation Of Escherichia Coli Translation By The Specific Inactivation Of TrnaGly Under Oxidative Stress, Lorenzo Eugenio Leiva, Andrea Pincheira, Sara Elgamal, Sandra D. Kienast, Verónica Bravo, Johannes Leufken, Daniela Gutiérrez, Sebastian A. Leidel, Michael Ibba, Assaf Katz

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Bacterial oxidative stress responses are generally controlled by transcription factors that modulate the synthesis of RNAs with the aid of some sRNAs that control the stability, and in some cases the translation, of specific mRNAs. Here, we report that oxidative stress additionally leads to inactivation of tRNA^Gly in Escherichia coli, inducing a series of physiological changes. The observed inactivation of tRNA^Gly correlated with altered efficiency of translation of Gly codons, suggesting a possible mechanism of translational control of gene expression under oxidative stress. Changes in translation also depended on the availability of glycine, revealing a mechanism whereby bacteria …

Structural Analysis Of Protein Therapeutics Using Covalent Labeling – Mass Spectrometry, Patanachai Limpikirati

Doctoral Dissertations

Using mass spectrometry (MS) to obtain information about a higher order structure of protein requires that a protein’s structural properties are encoded into the mass of that protein. Covalent labeling (CL) with reagents that can irreversibly modify solvent accessible amino acid side chains is an effective way to encode structural information into the mass of a protein, as this information can be read-out in a straightforward manner using standard MS-based proteomics techniques. The differential reactivity of proteins under two or more conditions can be used to distinguish protein topologies, conformations, and/or binding sites. CL-MS methods have been effectively used for …

Translational Regulation Of Environmental Adaptation In Bacteria, Rodney Tollerson Ii, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Bacteria must rapidly respond to both intracellular and environmental changes to survive. One critical mechanism to rapidly detect and adapt to changes in environmental conditions is control of gene expression at the level of protein synthesis. At each of the three major steps of translation—initiation, elongation, and termination—cells use stimuli to tune translation rate and cellular protein concentrations. For example, changes in nutrient concentrations in the cell can lead to translational responses involving mechanisms such as dynamic folding of riboswitches during translation initiation or the synthesis of alarmones, which drastically alter cell physiology. Moreover, the cell can fine-tune the levels …

Alternative Polyadenylation Modulates Expression Of Pro-Fibrotic Proteins And Contributes To Lung Fibrosis, Junsuk Ko

Dissertations & Theses (Open Access)

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease which affects about 5 to 8 million individuals in the world. Despite the high prevalence, there is currently no cure for IPF, and the cause of this disease is still unclear. Our laboratory and collaborators have shown that nudix hydrolase 21 (NUDT21, which is also known as cleavage factor 25, CFIm25) is a key regulator of alternative polyadenylation (APA). NUDT21 depletion causes 3’UTR shortening via APA leading to enhanced mRNA stability and protein translation. This NUDT21 reduction promotes tumor growth in glioblastoma by enhancing expression of oncogenes. Cancer and IPF share …

A Study Of The Antioxidant Versus Pro-Oxidant Nature Of The Amyloid Beta Peptide And An Analysis Of The Natural Products, Isorhamnetin And Narignenin, As Antioxidants, Kaylee Holmes

Honors Theses

Alzheimer’s disease is a neurodegenerative disorder with no cure. Due to the widespread effects of this disease, abundant research efforts have gone towards finding a cure. The amyloid beta (Ab) peptide has been shown to be a potential cause of the disease due to destructive effects on tissues that it can have both by itself and through reactive oxygen species (ROS) generation. This study was performed in order to assess the structural properties of Ab₄₂monomers, fibrils and oligomers, to assess the antioxidant versus pro-oxidant behavior of the Ab peptide, and to assess the antioxidant nature of the natural …

Aminoacyl-Trna Synthetases, Miguel Angel Rubio Gomez, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The aminoacyl-tRNA synthetases are an essential and universally distributed family of enzymes that plays a critical role in protein synthesis, pairing tRNAs with their cognate amino acids for decoding mRNAs according to the genetic code. Synthetases help to ensure accurate translation of the genetic code by using both highly accurate cognate substrate recognition and stringent proofreading of noncognate products. While alterations in the quality control mechanisms of synthetases are generally detrimental to cellular viability, recent studies suggest that in some instances such changes facilitate adaption to stress conditions. Beyond their central role in translation, synthetases are also emerging as key …

Targeting Trna-Synthetase Interactions Towards Novel Therapeutic Discovery Against Eukaryotic Pathogens, Paul Kelly, Fatemeh Hadi-Nezhad, Dennis Y. Liu, Travis J. Lawrence, Roger G. Linington, Michael Ibba, David H. Ardell

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The development of chemotherapies against eukaryotic pathogens is especially challenging because of both the evolutionary conservation of drug targets between host and parasite, and the evolution of strain-dependent drug resistance. There is a strong need for new nontoxic drugs with broad-spectrum activity against trypanosome parasites such as Leishmania and Trypanosoma. A relatively untested approach is to target macromolecular interactions in parasites rather than small molecular interactions, under the hypothesis that the features specifying macromolecular interactions diverge more rapidly through coevolution. We computed tRNA Class-Informative Features in humans and independently in eight distinct clades of trypanosomes, identifying parasite-specific informative features, …

Validity Of Plasma Collection Cards For Ferritin Assessment—A Proof-Of-Concept Study, Karsten Koehler, Eileen Marks-Nelson, Camila Pereira Braga, Safiya E. Beckford, Jiri Adamec

Department of Biochemistry: Faculty Publications

Objectives: Iron depletion is common around the world and among certain risk groups in developed countries. The overall purpose was to test the suitability of a novel plasma collection card for minimally invasive iron status assessment.

Methods: Twenty participants (10 f/10 m) participated in this cross-sectional study. Ferritin and hemoglobin were measured from blood collected from a forearm vein, serving as reference method. Blood was also collected from the fingertip using the NoviplexTM Plasma Prep Card as well as capillary collection tubes.

Results: There was substantial concordance between ferritin measured from samples collected via NoviplexTM and venous ferritin (concordance correlation …

Alanyl-Trna Synthetase Quality Control Prevents Global Dysregulation Of The Escherichia Coli Proteome, Paul Kelly, Nicholas Backes, Kyle Mohler, Christopher Buser, Arundhati Kavoor, Jesse Rinehart, Gregory Phillips, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Mechanisms have evolved to prevent errors in replication, transcription, and translation of genetic material, with translational errors occurring most frequently. Errors in protein synthesis can occur at two steps, during tRNA aminoacylation and ribosome decoding. Recent advances in protein mass spectrometry have indicated that previous reports of translational errors have potentially underestimated the frequency of these events, but also that the majority of translational errors occur during ribosomal decoding, suggesting that aminoacylation errors are evolutionarily less tolerated. Despite that interpretation, there is evidence that some aminoacylation errors may be regulated, and thus provide a benefit to the cell, while others …

Protein Detection And Structural Characterization By Mass Spectrometry Using Supramolecular Assemblies And Small Molecules, Bo Zhao

Doctoral Dissertations

Mass spectrometry (MS) has played an increasingly prominent role in proteomics and structure biology because it shows superior capabilities in identification, quantification and structural characterization of proteins. To realize its full potential in protein analysis, significant progress has been made in developing innovative techniques and reagents that can couple to MS detection. This dissertation demonstrates the use of polymeric supramolecular assemblies for enhanced protein detection in complex biological mixtures by MS. An amphiphilic random co-polymer scaffold is developed to form functional supramolecular assemblies for protein/ peptide enrichment. The influences of charge density and functional group pK_a on host-guest interactions …

The Fitness Landscape Of The African Salmonella Typhimurium St313 Strain D23580 Reveals Unique Properties Of The Pbt1 Plasmid, Rocío Canals, Roy R. Chaudhuri, Rebecca E. Steiner, Siân V. Owen, Natalia Quinones-Olvera, Melita A. Gordon, Michael Baym, Michael Ibba, Jay C. D. Hinton

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

We have used a transposon insertion sequencing (TIS) approach to establish the fitness landscape of the African Salmonella enterica serovar Typhimurium ST313 strain D23580, to complement our previous comparative genomic and functional transcriptomic studies. We used a genome-wide transposon library with insertions every 10 nucleotides to identify genes required for survival and growth in vitro and during infection of murine macrophages. The analysis revealed genomic regions important for fitness under two in vitro growth conditions. Overall, 724 coding genes were required for optimal growth in LB medium, and 851 coding genes were required for growth in SPI-2-inducing minimal medium. These …

Microvascular Stenosis In Critical Limb Ischemia: Role Of Partial Endothelial To Mesenchymal Transition, Jacqueline M. Chevalier

Electronic Thesis and Dissertation Repository

Critical limb ischemia (CLI) is a widespread and debilitating manifestation of atherosclerosis. Unfortunately, revascularization strategies are often precluded or unsuccessful, resulting in amputation. A major reason for treatment failure is likely co-existing abnormalities in ­­the microvasculature. However, the specific microvascular defects present in end-stage PAD in humans remain unknown.

The purpose of this study was to delineate abnormalities in the microvascular wall in the critically ischemic skeletal muscle of patients with CLI.

To elucidate the microvascular landscape in CLI, we studied human tibialis anterior and gastrocnemius muscles harvested from below-knee amputations of 10 individuals with CLI. Control muscles are from …

Translational Control Of Antibiotic Resistance, Anne Witzky, Rodney Tollerson Ii, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Many antibiotics available in the clinic today directly inhibit bacterial translation. Despite the past success of such drugs, their efficacy is diminishing with the spread of antibiotic resistance. Through the use of ribosomal modifications, ribosomal protection proteins, translation elongation factors and mistranslation, many pathogens are able to establish resistance to common therapeutics. However, current efforts in drug discovery are focused on overcoming these obstacles through the modification or discovery of new treatment options. Here, we provide an overview for common mechanisms of resistance to translation-targeting drugs and summarize several important breakthroughs in recent drug development.

The Effects Of Eicosapentaenoic Acid (Epa) And Docosahexaenoic Acid (Dha) On Brown Adipogenesis In Stem Cell Culture, Darynne Dahlem

Animal Science Undergraduate Honors Theses

Polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are major maternal dietary supplements due to their positive benefits on neurological tissue growth during the first 12 weeks of gestation. Previous studies show that EPA and DHA inhibit muscle formation but promote adipogenesis. However, no research has addressed the question whether high intake of EPA and DHA affects brown fat development during gestation. The objective of this study was to measure the effect of EPA and DHA supplement on brown adipogenesis and potential pathways related to mitochondrial biosynthesis using fibroblasts as in vitro model. Using Oil-Red-O staining …