Christopher Anthony Dieni
Christopher Anthony Dieni
Metabolic biochemist with broad expertise in research, training, and project design
About
25
Publications
7,598
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Introduction
I have roughly two decades of hands-on experience in a number of research laboratories. These include labs in startup biotech industries (Micropharma Ltd), research-intensive universities (Penn State), mid-sized comprehensive universities (University of Windsor, Carleton University, Concordia University), and primarily-undergraduate institutions (Saint Michael's College, Spring Hill College, Colorado Mesa University, Ursinus College, Mount Allison University).
Additional affiliations
August 2022 - June 2024
August 2021 - May 2022
August 2019 - June 2021
Education
September 2004 - August 2008
September 2001 - May 2004
September 1999 - May 2001
Publications
Publications (25)
Catecholic compounds, characterized by their distinct dihydroxybenzene functional groups, are recognized for their diverse biological roles and emerging therapeutic potential. Despite significant advances in understanding their biotransformation and chemical reactivity, the potential for enzyme-independent reactions of catechols under physiological...
In terrestrial vertebrates, inhalation of airborne engineered nanomaterials (ENMs) can trigger an oxidative stress response, subsequently leading to vascular inflammation and cardiorespiratory dysfunction. Direct or indirect oxidative stress is frequently cited as a mechanism of ENM toxicity in aquatic organisms, and a growing body of evidence sugg...
Background
Catechol, 1,2-dihydroxybenzene, prepared through bacterial biotransformation from higher order polyphenols, has been proposed to regulate carbohydrate metabolism, especially in the context of type 2 diabetes. This review aims to contextualize this finding. It describes the bacterial biosynthesis of catechol both from glucose, and as a de...
Engineered nanomaterials (ENMs) are a diverse class of materials whose distinct properties make them desirable in a multitude of applications. The proliferation of nanotoxicology research has improved our understanding of ENM toxicity, but an under appreciation for their potential to interfere with biochemical assays has hampered progress in the fi...
Citrated Sprague–Dawley rat blood plasma was used as a biologically relevant exposure medium to assess the acellular toxic potential of two metal oxide engineered nanomaterials (ENMs), zinc oxide (nZnO), and cerium oxide (nCeO2). Plasma was incubated at 37 °C for up to 48 h with ENM concentrations ranging between 0 and 200 mg/L. The degree of ENM-i...
Acute exposure to commercially-relevant zinc oxide nanoparticles (nZnO) can alter heart function and induce a cellular stress response in gill tissue of the white sucker (Catostomus commersonii), a freshwater teleost fish. The current study aimed to identify potential mechanisms underlying the cardiorespiratory effects of nZnO exposure and to chara...
Metal oxide nanomaterials can cause oxidative, cardiorespiratory, and osmoregulatory stress in freshwater fish. In contrast, cerium oxide nanoparticles (nCeO2) can have antioxidant effects but their aquatic toxicity has not been fully characterized. Heart rate and heart rate variability were followed in white sucker (Catostomus commersonii) acutely...
The inhalation of zinc oxide engineered nanomaterials (ENMs) has been linked to cardiorespiratory dysfunction in mammalian models but the effects of aquatic ENM exposure on fish have not been fully investigated. Nano-zinc oxide (nZnO) is widely used in consumer products such as sunscreens and can make its way into aquatic ecosystems from domestic a...
The wood frog, Rana sylvatica, survives whole-body freezing and thawing each win-ter. The extensive adaptations required at the biochemical level are facilitated by alterations to signaling pathways, including the insulin/Akt and AMPK pathways. Past studies investigating changing tissue-specific patterns of the second messenger IP 3 in adapted frog...
Liver toxicity of commercially relevant zinc oxide nanoparticles (nZnO) was assessed in a benthic freshwater cypriniform, the white sucker (Catostomus commersonii). Exposure to nZnO caused several changes in levels of liver enzyme activity, antioxidants, and lipid peroxidation end products consistent with an oxidative stress response. Aconitase act...
The wood frog, Rana sylvatica , survives whole-body freezing and thawing each winter. The extensive adaptations required at the biochemical level are facilitated by alterations to signaling pathways, including the insulin/Akt and AMPK pathways. Past studies investigating changing tissue-specific patterns of the second messenger IP 3 in adapted frog...
The wood frog, Rana sylvatica, survives whole-body freezing and thawing each winter. The extensive adaptations required at the biochemical level are facilitated by alterations to signaling pathways, including the insulin/Akt and AMPK pathways. Past studies investigating changing tissue-specific patterns of the second messenger IP 3 in adapted frogs...
Suspensions of bovine serum albumin (BSA) and spherical gold nanoparticles were analyzed to determine if gold nanoparticles (nAu) affect the ligand binding properties of BSA. A range of diameters of nAu with a carboxylic acid capping agent (nAu-cap) were tested, along with nanoparticles conjugated to amine (nAu-NH 3 +) and carboxyl (nAu-COO -) func...
The use of percutaneous medical devices often results in nosocomial infections. Attachment of microorganisms to the surfaces
of these medical devices triggers biofilm formation, which presents significant complications to the health of a patient and
may lead to septicemia, thromboembolism, or endocarditis if not correctly treated. Although several...
Metabolic signaling coordinates the transition by hibernating mammals from euthermia into profound torpor. Organ-specific responses by activated p38 mitogen activated protein kinase (MAPK) are known to contribute to this transition. Therefore, we hypothesized that the MAPK-activated protein kinase-2 (MAPKAPK2), a downstream target of p38 MAPK, woul...
The terrestrial anuran Rana sylvatica tolerates extended periods of whole-body freezing during the winter. Freezing survival is facilitated by extensive glycogen hydrolysis and distribution of high concentrations of the cryoprotectant glucose into blood and all tissues. As glycogenesis is both an energy-expensive process and counter-productive to m...
Hexokinase (HK) was isolated from hind leg skeletal muscle of the wood frog, Rana sylvatica, a freeze tolerant species that uses glucose as a cryoprotectant. Analysis of kinetic parameters (K(m) and V(max)) of HK showed significant increases in K(m) glucose (from 144 ± 4.4 to 248 ± 1 2.0 μM) and K(m) ATP (from 248 ± 8.5 to 330 ± 20.9 μM), as well a...
Glucose-6-phosphate dehydrogenase (G6PDH) and the pentose phosphate pathway play a key role in reductive biosynthesis and antioxidant defense, while diverting glucose from other cellular functions. G6PDH was isolated from liver of the wood frog, Rana sylvatica, a freeze tolerant species that uses glucose as a cryoprotectant. Analysis of kinetic par...
Creatine kinase (CK) was analyzed from skeletal muscle of wood frogs, Rana sylvatica, a species that survives natural whole body freezing during the winter months. Muscle CK activity increased by 35% and apparent Km creatine decreased by 29% when frogs froze. Immunoblotting analysis showed that this activity increase was not due to a change in tota...
Akt (or protein kinase B) plays a central role in coordinating growth, survival and anti-apoptotic responses in cells and we hypothesized that changes in Akt activity and properties would aid the reprioritization of metabolic functions that occurs during mammalian hibernation. Akt was analyzed in skeletal muscle and liver of Richardson's ground squ...
The wood frog, Rana sylvatica, is one of a few vertebrate species that have developed natural freeze tolerance, surviving days or weeks with 65-70% of its total body water frozen in extracellular ice masses. Frozen frogs exhibit no vital signs and their organs must endure multiple stresses, particularly long term anoxia and ischemia. Maintenance of...
Questions
Questions (4)
Hello all,
I have recently embarked into mammalian cell culture using mutiwell culture plates (e.g. 6-well plates, 12-well plates, etc.) as opposed to previous studies where I have used individual flasks (e.g. T25, T75, etc.). When using flasks, I was accustomed to lysing cells in somewhat of a more "low-throughput" method in a lysis buffer containing 1% Triton X-100, applying mechanical shearing force by passing the cells through an 18G needle.
Moving to multiwell culture plates, the needle method is quite tedious. Having to pass the cells from each well through an 18G needle, one at a time, is very time consuming and counterbalances much of the time that is saved by using a multiwell plate in the first place.
Is there another method that is friendlier to "high-throughput" multiwell plates, that anyone might suggest which lyses cells without having to pass them through a needle one-by-one -- yet does not interfere with downstream assays for protein concentration?
Thanks in advance,
Chris Dieni
Hello all,
I'm currently working with undergraduate student-researchers (there are no graduate students at my university) to purify and characterize the drug targetability of glucokinase from pig liver. We thought it would be a fairly feasible project considering the limited hours that student-researchers can invest (given their abundant courseloads) and the limited infrastructure in a primarily-undergraduate institution.
After several weeks of lab work, it would appear that what we thought was glucokinase activity may in fact be another enzyme. The enzyme activity seems to run perfectly fine (even better, in fact) despite omitting ATP from the assay below:
Glucose + ATP --> glucose-6-phosphate + ADP
glucose-6-phosphate + NADP+ --> 6-phosphoglucono-delta-lactone + NADPH + H+
I've wracked my brain trying to figure out why the enzyme activity would be as high (or higher!) in the absence of ATP in the enzyme assay, and the only conclusion I can come up with is that we're actually somehow assaying glucose dehydrogenase, with a reaction of glucose + NADP+ --> glucono-delta-lactone + NADPH + H+.
Has anyone encountered this conundrum and been able to resolve it?
Before you answer, allow me to please add the following:
- We do NOT have access to SDS-PAGE methodologies to determine the molecular weight of the enzyme in question; in fact, we haven't gotten significantly far in our purification beyond a resuspension of the 40% ammonium sulfate-precipitated pellet.
- We do NOT have access to the resources and consumables needed to express and purify recombinant proteins -- hence why we're working with pig livers.
Hello ResearchGate community,
I would like to carry out some protein-ligand binding assays. Normally, in the past, I would have simply used a fluorophore -- such as ANS -- and measured the change in fluorescence intensity as ANS would bind to a protein, such as BSA.
At present, I have minimal (if any) fluorescence capabilities. I'm looking for a commercially-available ligand/probe that will experience a shift in absorbance spectrum upon binding to a protein.
So far, I've only found a single publication, detailing the use of Neutral Red (a pH-sensitive dye) as a ligand capable of binding to riboflavin protein: https://pubs.acs.org/doi/full/10.1021/ed1000125?src=recsys
I know that fluorescence is typically the norm -- but I wonder if anyone else out there has experience with absorbance as a tool to measure ligand binding.
Kind regards,
Chris Dieni
