The Frequency of Symptoms in Patients With a Diagnosis of Degenerative Cervical Myelopathy: Results of a Scoping Review.

STUDY DESIGN: Delayed diagnosis of degenerative cervical myelopathy (DCM) is associated with reduced quality of life and greater disability. Developing diagnostic criteria for DCM has been identified as a top research priority. OBJECTIVES: This scoping review aims to address the following questions: What is the diagnostic accuracy and frequency of clinical symptoms in patients with DCM? METHODS: A scoping review was conducted using a database of all primary DCM studies published between 2005 and 2020. Studies were included if they (i) assessed the diagnostic accuracy of a symptom using an appropriate control group or (ii) reported the frequency of a symptom in a cohort of DCM patients. RESULTS: This review identified three studies that discussed the diagnostic accuracy of various symptoms and included a control group. An additional 58 reported on the frequency of symptoms in a cohort of patients with DCM. The most frequent and sensitive symptoms in DCM include unspecified paresthesias (86%), hand numbness (82%) and hand paresthesias (79%). Neck and/or shoulder pain was present in 51% of patients with DCM, whereas a minority had back (19%) or lower extremity pain (10%). Bladder dysfunction was uncommon (38%) although more frequent than bowel (23%) and sexual impairment (4%). Gait impairment is also commonly seen in patients with DCM (72%). CONCLUSION: Patients with DCM present with many different symptoms, most commonly sensorimotor impairment of the upper extremities, pain, bladder dysfunction and gait disturbance. If patients present with a combination of these symptoms, further neuroimaging is indicated to confirm the diagnosis of DCM.

The value of Clinical signs in the diagnosis of Degenerative Cervical Myelopathy - A Systematic review and Meta-analysis.

STUDY DESIGN: Delayed diagnosis of degenerative cervical myelopathy (DCM) is likely due to a combination of its subtle symptoms, incomplete neurological assessments by clinicians and a lack of public and professional awareness. Diagnostic criteria for DCM will likely facilitate earlier referral for definitive management. OBJECTIVES: This systematic review aims to determine (i) the diagnostic accuracy of various clinical signs and (ii) the association between clinical signs and disease severity in DCM? METHODS: A search was performed to identify studies on adult patients that evaluated the diagnostic accuracy of a clinical sign used for diagnosing DCM. Studies were also included if they assessed the association between the presence of a clinical sign and disease severity. The QUADAS-2 tool was used to evaluate the risk of bias of individual studies. RESULTS: This review identified eleven studies that used a control group to evaluate the diagnostic accuracy of various signs. An additional 61 articles reported on the frequency of clinical signs in a cohort of DCM patients. The most sensitive clinical tests for diagnosing DCM were the Tromner and hyperreflexia, whereas the most specific tests were the Babinski, Tromner, clonus and inverted supinator sign. Five studies evaluated the association between the presence of various clinical signs and disease severity. There was no definite association between Hoffmann sign, Babinski sign or hyperreflexia and disease severity. CONCLUSION: The presence of clinical signs suggesting spinal cord compression should encourage health care professionals to pursue further investigation, such as neuroimaging to either confirm or refute a diagnosis of DCM.

MoveStrong at home: a feasibility study of a model for remote delivery of functional strength and balance training combined with nutrition education for older pre-frail and frail adults.

Exercise and nutrition interventions are often recommended for frailty; however, effective strategies are required for real-world implementation. Our primary aim was to assess the feasibility and acceptability of telephone and virtual delivery of MoveStrong, an 8-week exercise and nutrition program with a 4-week follow-up for older pre-frail and frail adults. A priori criteria for success included: recruitment (≥25/12 weeks), retention at follow-up (≥80%), and adherence to exercise and nutrition sessions (≥70%). We recruited community-dwelling Ontario residents; ≥60 years, ≥1 chronic condition, ≥1 FRAIL scale score. Participants received mailed materials, a personalized exercise program, 11 remote one-on-one training sessions with an exercise physiologist and 3 online dietitian-led nutrition education sessions. We completed exploratory analyses of secondary outcomes including physical function and dietary protein intake. Semi-structured interviews supported program evaluation. In total, 30 participants were enrolled. 28 (93%) participants completed program and follow-up assessments. Adherence to exercise and nutrition sessions (CI) was 84% (77%-91%) and 82% (70%-93%) respectively. At program end and follow-up [mean change (CI)], significant improvements were measured in 30-second chair stand test [3.50 (1.12-5.86), 4.54 (1.94-7.13) chair stands] and dietary protein intake [12.9 (5.7-20.0), 9.2 (0.4-18.1) g]. Overall, participants were satisfied with program delivery. Trial registration number: NCT04663685.

Encouraging older adults with pre-frailty and frailty to "MoveStrong": an analysis of secondary outcomes for a pilot randomized controlled trial. / Encourager les personnes âgées souffrant de préfragilité et de fragilité à participer au programme d'exercice et de nutrition « MoveStrong ¼ : analyse des résultats secondaires d'un essai pilote comparatif randomisé.

BACKGROUND: This 8-week pilot stepped-wedge randomized controlled trial evaluated the MoveStrong program for teaching adults who have frailty/pre-frailty about balance and functional strength training and sufficient protein intake to prevent falls and improve mobility. METHODS: We recruited individuals aged 60 years and over, with a FRAIL scale score of 1 or higher and at least one chronic condition, who were not currently strength training. The program included 16 exercise physiologist-led hour-long group sessions and two dietitian-led hour-long nutrition sessions. We analyzed secondary outcomes-weight, gait speed, grip strength, physical capacity (fatigue levels), sit-to-stand functioning, dynamic balance, health-related quality of life (HRQoL), physical activity levels and protein intake-using a paired t test and a generalized estimating equation (GEE). RESULTS: Of 44 participants (mean [SD] age 79 [9.82] years), 35 were pre-frail and 9 were frail. At follow-up, participants had significantly improved grip strength (1.63 kg, 95% CI: 0.62 to 2.63); sit-to-stand functioning (2 sit-to-stands, 95% CI: 1 to 3); and dynamic balance (1.68 s, 95% CI: 0.47 to 2.89). There were no significant improvements in gait speed, HRQoL index scores, self-rated health, physical activity levels (aerobic activity and strength training) or protein intake. GEE analysis revealed an interaction between exposure to MoveStrong and gait speed, sit-to-stand functioning, dynamic balance and HRQoL index scores. The total cost to administer the program and purchase equipment was CAD 14 700, equivalent to CAD 377 per participant. CONCLUSION: Exploratory analyses suggest MoveStrong exercises may improve gait speed, sit-to-stand functioning, dynamic balance and HRQoL index scores in older individuals who are frail and pre-frail.

Establishing the Socio-Economic Impact of Degenerative Cervical Myelopathy Is Fundamental to Improving Outcomes [AO Spine RECODE-DCM Research Priority Number 8].

STUDY DESIGN: Literature Review (Narrative). OBJECTIVE: To contextualize AO Spine RECODE-DCM research priority number 5: What is the socio-economic impact of DCM? (The financial impact of living with DCM to the individual, their supporters, and society as a whole). METHODS: In this review, we introduce the methodology of health-economic investigation, including potential techniques and approaches. We summarize the current health-economic evidence within DCM, so far focused on surgical treatment. We also cover the first national estimate, in partnership with Myelopathy.org from the United Kingdom, of the cost of DCM to society. We then demonstrate the significance of this question to advancing care and outcomes in the field. RESULTS: DCM is a common and often disabling condition, with a significant lack of recognition. While evidence demonstrates the cost-effectives of surgery, even among higher income countries, health inequalities exist. Further the prevalent residual disability in myelopathy, despite treatment affects both the individual and society as a whole. A report from the United Kingdom provides the first cost-estimate to their society; an annual cost of ∼£681.6 million per year, but this is likely a significant underestimate. CONCLUSION: A clear quantification of the impact of DCM is needed to raise the profile of a common and disabling condition. Current evidence suggests this is likely to be globally substantial.

Improving Awareness Could Transform Outcomes in Degenerative Cervical Myelopathy [AO Spine RECODE-DCM Research Priority Number 1].

STUDY DESIGN: Literature Review (Narrative). OBJECTIVE: To introduce the number one research priority for Degenerative Cervical Myelopathy (DCM): Raising Awareness. METHODS: Raising awareness has been recognized by AO Spine RECODE-DCM as the number one research priority. This article reviews the evidence that awareness is low, the potential drivers, and why this must be addressed. Case studies of success from other diseases are also reviewed, drawing potential parallels and opportunities for DCM. RESULTS: DCM may affect as many as 1 in 50 adults, yet few will receive a diagnosis and those that do will wait many years for it. This leads to poorer outcomes from surgery and greater disability. DCM is rarely featured in healthcare professional training programs and has received relatively little research funding (<2% of Amyotrophic Lateral Sclerosis or Multiple Sclerosis over the last 25 years). The transformation of stroke and acute coronary syndrome services, from a position of best supportive care with occasional surgery over 50 years ago, to avoidable disability today, represents transferable examples of success and potential opportunities for DCM. Central to this is raising awareness. CONCLUSION: Despite the devastating burden on the patient, recognition across research, clinical practice, and healthcare policy are limited. DCM represents a significant unmet need that must become an international public health priority.

The MoveStrong program for promoting balance and functional strength training and adequate protein intake in pre-frail older adults: A pilot randomized controlled trial.

BACKGROUND: Balance and functional strength training can improve muscle strength and physical functioning outcomes and decrease the risk of falls in older adults. To maximize the benefits of strength training, adequate protein intake is also important. However, the number of older individuals that consume enough protein or routinely engage in strength training remains low at less than 5% and even lower for activities that challenge balance. Our primary aim was to assess the feasibility of implementing a model (MoveStrong) of service delivery to teach older adults about balance and functional strength training and methods to increase protein intake. METHODS: This study was a closed cohort stepped wedge randomized controlled trial. We recruited individuals ≥60 years considered pre-frail or frail with at least one chronic condition who were not currently engaging in regular strength training from Northern (rural) and Southern (urban) Ontario sites in Canada. The primary outcome was feasibility of implementation, defined by recruitment, retention, and adherence, and safety (defined by monitoring adverse events). We also reported participants' and providers' experience with MoveStrong, adaptations to the model based on participant's and provider's experience, and program fidelity. RESULTS: We recruited 44 participants to the study and the average adherence rate was 72% with a retention of 71%. The program had a high-fidelity score. One person experienced a fall-related injury during exercise, while two other participants reported pain during certain activities. Five individuals experienced injuries or health problems that were not related to the program. Suggestions for future trials include modifying some exercises, exploring volunteer assistance, increasing the diversity of participants enrolled, and considering a different study design. CONCLUSIONS: Our pilot trial demonstrates the feasibility of recruitment and adherence for a larger multisite RCT of balance and functional strength training with attention to protein intake in pre-frail and frail older adults.

Boronated Condensed DNA as a Heterochromatic Radiation Target Model.

The compound 4-dihydroxyboryl-l-phenylalanine (BPA) has found use in clinical trials of boron neutron capture therapy (BNCT). Here, we have examined the interaction with DNA of an amide-blocked BPA derivative of hexa-l-arginine (Ac-BPA-Arg6-NH2). Physical and spectroscopic assays show that this peptide binds to and condenses DNA. The resulting condensates are highly resistant to the effects of nuclease incubation (68-fold) and gamma (38-fold) irradiation. Radioprotection was modeled by Monte Carlo track structure simulations of DNA single strand breaks (SSBs) with TOPAS-nBio. The differences between experimental and simulated SSB yields for uncondensed and condensed DNAs were ca. 2 and 18%, respectively. These observations indicate that the combination of a plasmid DNA target, the BPA-containing peptide, and track structure simulation provides a powerful approach to characterize DNA damage by the high-LET radiation associated with neutron capture on boron.

Fall prevention interventions for older community-dwelling adults: systematic reviews on benefits, harms, and patient values and preferences.

BACKGROUND: An estimated 20-30% of community-dwelling Canadian adults aged 65 years or older experience one or more falls each year. Fall-related injuries are a leading cause of hospitalization and can lead to functional independence. Many fall prevention interventions, often based on modifiable risk factors, have been studied. Apart from the magnitude of the benefits and harms from different interventions, the preferences of older adults for different interventions as well as the relative importance they place on the different potential outcomes may influence recommendations by guideline panels. These reviews on benefits and harms of interventions, and on patient values and preferences, will inform the Canadian Task Force on Preventive Health Care to develop recommendations on fall prevention for primary care providers. METHODS: To review the benefits and harms of fall prevention interventions, we will update a previous systematic review of randomized controlled trials with adaptations to modify the classification of interventions and narrow the scope to community-dwelling older adults and primary-care relevant interventions. Four databases (MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Ageline), reference lists, trial registries, and relevant websites will be searched, using limits for randomized trials and date (2016 onwards). We will classify interventions according to the Prevention of Falls Network Europe (ProFANE) Group's taxonomy. Outcomes include fallers, falls, injurious falls, fractures, hip fractures, institutionalization, health-related quality of life, functional status, and intervention-related adverse effects. For studies not included in the previous review, screening, study selection, data extraction on outcomes, and risk of bias assessments will be independently undertaken by two reviewers with consensus used for final decisions. Where quantitative analysis is suitable, network or pairwise meta-analysis will be conducted using a frequentist approach in Stata. Assessment of the transitivity and coherence of the network meta-analyses will be undertaken. For the reviews on patient preferences and outcome valuation (relative importance of outcomes), we will perform de novo reviews with searches in three databases (MEDLINE, PsycInfo, and CINAHL) and reference lists for cross-sectional, longitudinal quantitative, or qualitative studies published from 2000. Selection, data extraction, and risk of bias assessments suitable for each study design will be performed in duplicate. The analysis will be guided by a narrative synthesis approach, which may include meta-analysis for health-state utilities. We will use the CINeMa approach to a rate the certainty of the evidence for outcomes on intervention effects analyzed using network meta-analysis and the GRADE approach for all other outcomes. DISCUSSION: We will describe the flow of literature and characteristics of all studies and present results of all analyses and summary of finding tables. We will compare our findings to others and discuss the limitations of the reviews and the available literature. SYSTEMATIC REVIEW REGISTRATION: This protocol has not been registered.

DNA Condensation with a Boron-Containing Cationic Peptide for Modeling Boron Neutron Capture Therapy.

The amino acid derivative 4-borono-L-phenylalanine (BPA) has been used in the radiation medicine technique boron neutron capture therapy (BNCT). Here we have characterized its interaction with DNA when incorporated into a positively charged hexa-L-arginine peptide. This ligand binds strongly to DNA and induces its condensation, an effect which is attenuated at higher ionic strengths. The use of an additional tetra-L-arginine ligand enables the preparation of a DNA condensate in the presence of a negligible concentration of unbound boron. Under these conditions, Monte Carlo simulation indicates that >85% of energy deposition events resulting from thermal neutron irradiation derive from boron fission. The combination of experimental model systems and simulations that we describe here provides a valuable tool for accurate track structure modeling of the DNA damage produced by the high LET particles involved in BNCT.

Medication-related problems in individuals with spinal cord injury in a primary care-based clinic.

OBJECTIVE: To determine the frequency of medical problems, reason for referral/primary complaint, products used, medication-related problems, and polypharmacy in patients with spinal cord injury (SCI) seen at an interprofessional primary care mobility clinic. DESIGN: Retrospective review of medical records of patients with SCI for patient visits between August 2012 and March 2013. METHODS: Data were abstracted from medical records of patients with SCI. RESULTS: Of 74 patients who presented to the clinic, 19 had an SCI. Mean age was 46.7 years and 74% were male. Most frequent medical problems were depression/anxiety (37%), osteoporosis/osteopenia (26%), hypertension (21%), dyslipidemia (21%), and osteoarthritis (21%). Most common presenting complaints were pain (23%) and bowel/bladder issues (13%). Most common medication-related problems were untreated conditions (41%), ineffective medications (21%), adverse drug reactions (18%), and under- and over-dosage (each 9%). Patients with SCI most frequently used products to treat pain (68%), constipation (42%), muscle spasm (42%), hypertension (42%), and depression (37%). When including natural health products, vitamins and minerals, polypharmacy was seen in 74% of patients with SCI (63% when limited to prescription and over-the-counter medications). For patients with SCI in whose care a pharmacist collaborated, a mean of 3.2 medication-related problems per patient were identified compared with 1 per patient when the pharmacist was not involved. CONCLUSION: This study is the first to describe medication use, polypharmacy and medication-related problems in patients with SCI seen at an interprofessional primary care clinic. Use of high-risk medications, polypharmacy, and medication-related problems in patients with SCI suggest the need for collaborative interprofessional care that includes a pharmacist.

Synthesis and Catalytic Activity of Pluronic Stabilized Silver-Gold Bimetallic Nanoparticles.

In this report, we demonstrate a rapid, simple, and green method for synthesizing silver-gold (Ag-Au) bimetallic nanoparticles (BNPs). We used a novel modification to the galvanic replacement reaction by suspending maltose coated silver nanoparticles (NPs) in ≈ 2% aqueous solution of EO100PO65EO100 (Pluronic F127) prior to HAuCl4 addition. The Pluronic F127 stabilizes the BNPs, imparts biocompatibility, and mitigates the toxicity issues associated with other surfactant stabilizers. BNPs with higher Au:Ag ratios and, subsequently, different morphologies were successfully synthesized by increasing the concentration of gold salt added to the Ag NP seeds. These BNPs have enhanced catalytic activities than typically reported for monometallic Au or Ag NPs (∼ 2-10 fold) of comparable sizes in the sodium borohydride reduction of 4-nitrophenol. The 4-nitrophenol reduction rates were highest for partially hollow BNP morphologies.

Mechanistic investigation of seeded growth in triblock copolymer stabilized gold nanoparticles.

We report the seeded synthesis of gold nanoparticles (GNPs) via the reduction of HAuCl4 by (L31 and F68) triblock copolymer (TBP) mixtures. In the present study, we focused on [TBP]/[Au(III)] ratios of 1-5 (≈1 mM HAuCl4) and seed sizes ~20 nm. Under these conditions, the GNP growth rate is dominated by both the TBP and seed concentrations. With seeding, the final GNP size distributions are bimodal. Increasing the seed concentration (up to ~0.1 nM) decreases the mean particle sizes 10-fold, from ~1000 to 100 nm. The particles in the bimodal distribution are formed by the competitive direct growth in solution and the aggregative growth on the seeds. By monitoring kinetics of GNP growth, we propose that (1) the surface of the GNP seeds embedded in the TBP cavities form catalytic centers for GNP growth and (2) large GNPs are formed by the aggregation of GNP seeds in an autocatalytic growth process.

Radioprotective effects produced by the condensation of plasmid DNA with avidin and biotinylated gold nanoparticles.

The treatment of aqueous solutions of plasmid DNA with the protein avidin results in significant changes in physical, chemical, and biochemical properties. These effects include increased light scattering, formation of micron-sized particles containing both DNA and protein, and plasmid protection against thermal denaturation, radical attack, and nuclease digestion. All of these changes are consistent with condensation of the plasmid by avidin. Avidin can be displaced from the plasmid at higher ionic strengths. Avidin is not displaced from the plasmid by an excess of a tetra-arginine ligand, nor by the presence of biotin. Therefore, this system offers the opportunity to reversibly bind biotin-labeled species to a condensed DNA-protein complex. An example application is the use of biotinylated gold nanoparticles. This system offers the ability to examine in better detail the chemical mechanisms involved in important radiobiological effects. Examples include protein modulation of radiation damage to DNA, and radiosensitization by gold nanoparticles.

Yields of damage to C4' deoxyribose and to pyrimidines in pUC18 by the direct effect of ionizing radiation.

Our mechanistic understanding of damage formation in DNA by the direct effect relies heavily on what is known of free radical intermediates studied by EPR spectroscopy. Bridging this information to stable product formation requires methods with comparable sensitivities, a criterion met by the (32)P-post-labeling assay developed by Weinfeld and Soderlind, [Weinfeld,M. and Soderlind,K.-J.M. (1991) (32)P-Postlabeling detection of radiation-induced DNA damage: identification and estimation of thymine glycols and phosphoglycolate termini. Biochemistry, 30, 1091-1097] which when applied to the indirect effect, detected phosphoglycolate (pg) and thymine glycol (Tg). Here we applied this assay to the direct effect, measuring product yields in pUC18 films with hydration levels (Γ) of 2.5, 16 or 23 waters per nucleotide and X-irradiated at either 4 K or room temperature (RT). The yields of pg [G(pg)] for Γ ≈ 2.5 were 2.8 ± 0.2 nmol/J (RT) and 0.2 ± 0.3 nmol/J (4 K), which is evidence that the C4' radical contributes little to the total deoxyribose damage via the direct effect. The yield of detectable base damage [G(B*)] at Γ ≈ 2.5 was found to be 30.2 ± 1.0 nmol/J (RT) and 12.9 ± 0.7 nmol/J (4 K). While the base damage called B*, could be due to either oxidation or reduction, we argue that two reduction products, 5,6-dihydrouracil and 5,6-dihydrothymine, are the most likely candidates.

Modeling the influence of histone proteins on the sensitivity of DNA to ionizing radiation.

The DNA-binding proteins that are present in chromatin significantly affect the sensitivity of cells to ionizing radiation and to the radiation chemistry of DNA damage. The interaction between protein and DNA modifies the radiation chemistry of the latter. To model these processes, we have examined the effects of ionizing radiation on the minichromosome form of SV40 (which contains histone proteins arranged in nucleosomes) and also on plasmid DNA in the presence of lysozyme. Although high concentrations of lysozyme can bring about an extensive radioprotection by condensation of the plasmid, at lower levels it still produces significant radioprotective effects under conditions where this associative phase separation does not take place. The presence of histones or of lysozyme decreases the yield of modified guanines produced by ionizing radiation. Comparison with previous observations made with oligopeptides suggests that the mechanism responsible is electron donation to guanyl radicals in the DNA by tryptophan and tyrosine residues in the proteins. However, there was no evidence for DNA-protein crosslink formation.

Damage clusters after gamma irradiation of a nanoparticulate plasmid DNA peptide condensate.

We have gamma-irradiated plasmid DNA in aqueous solution in the presence of submillimolar concentrations of the ligand tetra-arginine. Depending upon the ionic strength, under these conditions, the plasmid can adopt a highly compacted and aggregated form which attenuates by some two orders of magnitude the yield of damage produced by the indirect effect. The yields of DNA single- and double-strand breaks (SSB and DSB) which result are closely comparable with those produced in living cells. The radical lifetimes, diffusion distances, and track structure are expected to be similarly well reproduced. After irradiation, the aggregation was reversed by adjusting the ionic conditions. The approximate spatial distribution of the resulting DNA damage was then assayed by comparing the increases in the SSB and DSB yields produced by a subsequent incubation with limiting concentrations of the eukaryotic base excision repair enzymes formamidopyrimidine-DNA N-glycosylase (the FPG protein) and endonuclease III. Smaller increases in DSB yields were observed in the plasmid target that was irradiated in the condensed form. By modeling the spatial distribution of DNA damage, this result can be interpreted in terms of a greater extent of damage clustering.

Free terminal amines in DNA-binding peptides alter the product distribution from guanine radicals produced by single electron oxidation.

PURPOSE: Electron deficient guanine radical species are major intermediates produced in DNA by the direct effect of ionizing irradiation. There is evidence that they react with amine groups in closely bound ligands to form covalent crosslinks. Crosslink formation is very poorly characterized in terms of quantitative rate and yield data. We sought to address this issue by using oligo-arginine ligands to model the close association of DNA and its binding proteins in chromatin. MATERIALS AND METHODS: Guanine radicals were prepared in plasmid DNA by single electron oxidation. The product distribution derived from them was assayed by strand break formation after four different post-irradiation incubations. RESULTS: We compared the yields of DNA damage produced in the presence of four ligands in which neither, one, or both of the amino and carboxylate termini were blocked with amides. Free carboxylate groups were unreactive. Significantly higher yields of heat labile sites were observed when the amino terminus was unblocked. The rate of the reaction was characterized by diluting the unblocked amino group with its amide blocked derivative. CONCLUSION: These observations provide a means to develop quantitative estimates for the yields in which these labile sites are formed in chromatin by exposure to ionizing irradiation.

DNA Binding Hydroxyl Radical Probes.

The hydroxyl radical is the primary mediator of DNA damage by the indirect effect of ionizing radiation. It is a powerful oxidizing agent produced by the radiolysis of water and is responsible for a significant fraction of the DNA damage associated with ionizing radiation. There is therefore an interest in the development of sensitive assays for its detection. The hydroxylation of aromatic groups to produce fluorescent products has been used for this purpose. We have examined four different chromophores which produce fluorescent products when hydroxylated. Of these, the coumarin system suffers from the fewest disadvantages. We have therefore examined its behavior when linked to a cationic peptide ligand designed to bind strongly to DNA.

Use of a coumarin-labeled hexa-arginine peptide as a fluorescent hydroxyl radical probe in a nanoparticulate plasmid DNA condensate.

Coumarin derivatives have found application as probes for the hydroxyl radical because one of the products of the reaction between them is a highly fluorescent umbelliferone. We have examined the interaction in aqueous solution between a cationic coumarin-labeled hexa-arginine peptide ligand and plasmid DNA, and compared after gamma irradiation the yields of products derived from both of them. At low ionic strengths, the ligand binds very tightly to the plasmid. Compared with the structurally similar 4-methylumbelliferone (phenolic pK(a) = 7.8), the fluorescent product derived from gamma irradiation of the coumarin labeled cationic peptide is significantly more acidic (pK(a) = 6.1), making it a very convenient probe for solutions of pH in the physiological range. The yield of this product is generally in excellent agreement over a wide range of conditions with that of the single strand break product produced by the reaction of the hydroxyl radical with the plasmid. Thus coumarin-labeled peptide ligands offer promise as hydroxyl radical probes for locations in close proximity to DNA.