| 1. |
- Graslund, S, et al.
(författare)
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Protein production and purification
- 2008
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Ingår i: Nature methods. - : Springer Science and Business Media LLC. - 1548-7105 .- 1548-7091. ; 5:2, s. 135-146
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Tidskriftsartikel (refereegranskat)
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| 22. |
- Demirdal, D, et al.
(författare)
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CHARACTERISATION OF SWEDISH MYOSITIS PATIENTS WITH ANTI-MDA5 AUTOANTIBODIES AND CORRELATION OF CLINICAL FEATURES WITH AUTOANTIBODY LEVELS
- 2022
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Ingår i: ANNALS OF THE RHEUMATIC DISEASES. - : BMJ. - 0003-4967 .- 1468-2060. ; 81, s. 751-752
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The association between anti-melanoma differentiation association protein 5 autoantibodies (aMDA5) and rapidly progressive interstitial lung disease (RP-ILD) in clinically amyopathic dermatomyositis is well established in Asian population cohorts. In western cohorts, ILD has been strongly associated with aMDA5 but data regarding RP-ILD have been more conflicting. It is also suggested that western cohorts have more pronounced myopathic features than Asian.ObjectivesTo characterise the disease manifestations of a Swedish aMDA5 positive idiopathic inflammatory myositis (IIM) cohort and to explore antigen reactivity of the MDA5 protein.MethodsFirst available serum samples collected from 28 consecutive patients with IIM and positive aMDA5 ever tested by ELISA, Line Blot (LB) or Immunoprecipitation, attending Karolinska University Hospital between 1999 and 2021, were included. Clinical data including presence of anti-SSA autoantibodies by ELISA or LB was retrieved retrospectively. An in-house ELISA was used to screen serum samples for reactivity against a recombinant MDA5 protein (rMDA5, aa A110-D1025, UniProt ID Q9BYX4) and seven MDA5-derived constructs containing different domains. Correlations between aMDA5 reactivity levels and clinical data were explored.ResultsNine patients showed no reactivity to any of the rMDA5 constructs by ELISA and were excluded from further analysis.Reactivity against rMDA5 was confirmed by ELISA in 19 patients (median 184.7 µg/mL (interquartile range (IQR) 277.07). The cohort included 13 male and 6 female patients, 94% Caucasian, with mean age at diagnosis of 41.05 years (standard deviation (SD) 10.5). Median disease duration at time of sampling was 0 months (IQR 1). All patients except one had signs of muscle involvement (muscle weakness, elevated muscle enzymes, muscle oedema or muscle biopsy consistent with myositis). At diagnosis 63.2% of patients reported muscle weakness (21.1 % had a manual muscle test 8 score <75). Dermatological findings were observed in 17/19 (89.7 %). During disease course nine patients (47.4%) had confirmed arthritis.ILD was diagnosed in 16/19 patients (84.2%), four of these (25%) developed a RP-ILD. One patient passed away due to RP-ILD and one required a lung transplant. Patients with ILD had a statistically significant higher mean age at diagnosis than those without (42.8.5 (SD 10.3) vs 31.3 (SD 4.7) years, p=0.02). Patients developing RP-ILD were not significantly older than patients with chronic ILD. Respiratory symptoms were reported by 75% of patients with ILD at time of diagnosis. The mean total lung capacity (TLC) of the ILD cohort was 68% (SD 17), mean diffusion capacity of carbon monoxide (DLCO) was 59% (SD 15) and mean forced vital capacity (FVC) was 62% (SD 19). There was a higher proportion of patients with CRP ≥ 3 times the reference range at diagnosis amongst patients with FVC <70 % than patients with FVC >70 % (88.9 % vs 16.7 %, p= 0.01).Ten patients (52.6%) had anti-SSA autoantibodies, all had ILD. Anti-SSA positive patients had a statistically significant lower TLC than those without (62% vs 79% respectively, p=0.04) and a lower FVC (57% vs 76% respectively, p=0.05).We found a weak non-statistically significant negative correlation between titres of aMDA5 and TLC, DLCO and FVC (Pearson coefficients -0.187, -0.289, -0.130 respectively). Frequency of ILD was higher in patients with aMDA5 titres >100 µg/mL than those with titers <100, but not statistically significant (81.3% vs 18.8%, respectively).ConclusionIn this Caucasian cohort of aMDA5 positive IIM patients, ILD was present in over 80% of patients, of these, one quarter had RP-ILD. Older patients were more likely to present with ILD. Anti-SSA positivity and higher CRP levels were associated with worse lung function. We found a weak negative correlation between aMDA5 titres and lung function tests, as well as a trend of higher frequency of ILD in patients with higher aMDA5 titres. Muscle and skin involvement were found in a high proportion of patients.AcknowledgementsD. Demirdal & E. Van Gompel contributed equally to this abstract.Disclosure of InterestsDeniz Demirdal: None declared, Eveline Van Gompel: None declared, Edvard Wigren: None declared, Maryam Dastmalchi: None declared, Begum Horuluoglu: None declared, Angeles Shunashy Galindo-Feria: None declared, Susanne Gräslund: None declared, Karine Chemin: None declared, Ingrid E. Lundberg Shareholder of: Roche and Novartis., Consultant of: Consulting fees from Corbus Pharmaceuticals Inc, Astra Zeneca, Bristol Myer´s Squibb, Corbus Pharmaceutical, EMD Serono Research & Development Institute, Argenx, Octapharma, Kezaar, Orphazyme, and Janssen, Grant/research support from: Research grants from Astra Zeneca, Antonella Notarnicola Speakers bureau: compensation for lecture at conference sponsored by Boehringer Ingelheim.
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| 23. |
- Doglia, S. M., et al.
(författare)
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QUINACRINE - SPECTROSCOPIC PROPERTIES AND INTERACTIONS WITH POLYNUCLEOTIDES
- 1993
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Ingår i: Biopolymers. - : Wiley. - 0006-3525 .- 1097-0282. ; 33:9, s. 1431-1442
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Tidskriftsartikel (refereegranskat)abstract
- The acridine dye quinacrine and its interactions with calf thymus DNA, poly(dA-dT).poly(dA-dT), and poly(dG-dC).poly(dG-dC) were studied by light absorption, linear dichroism, and fluorescence spectroscopy. The transition moments of quinacrine give rise to absorption bands polarized along the short axis (400-480-nm band), and the long axis (345-nm and 290-nm bands) of the molecule, respectively. Linear dichroism studies show that quinacrine intercalates into calf thymus DNA as well as into the polynucleotides, displaying fairly homogeneous binding to poly (dA-dT).poly(dA-dT), but more than one type of intercalation site for calf thymus DNA and poly(dG-dC).poly(dG-dC). Fluorescence spectroscopy shows that for free quinacrine the pK = 8.1 between the mono- and diprotonated states also remains unchanged in the excited state. Quinacrine bound to calf thymus DNA and polynucleotides exhibits light absorption typical for the intercalated diprotonated form. The fluorescence enhancement of quinacrine bound to poly (dA-dT).poly(dA-dT) may be due to shielding from water interactions involving transient H-bond formation. The fluorescence quenching in poly (dG-dC).poly (dG-dC) may be due to excited state electron transfer from guanine to quinacrine. (C) 1993 John Wiley & Sons, Inc.
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| 24. |
- Eriksson, M., et al.
(författare)
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LOCATION OF EXCIMER-FORMING ADDUCTS OF (+)-ANTI-BENZO A PYRENE DIOL EPOXIDE IN DNA
- 1993
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 115:5, s. 1639-1644
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Tidskriftsartikel (refereegranskat)abstract
- Covalent adducts of the carcinogenic polycyclic aromatic hydrocarbon (+)-anti-benzo[a]pyrene 7,8-dihydrodiol 9,10-epoxide ((+)-anti-BPDE) in polynucleotides have been studied by fluorescence spectroscopy. The pyrenyl chromophores of the BPDE adducts, linked by the C10 atom to the exocyclic nitrogen of guanine, interact in the photoexcited state, as evidenced by excimer fluorescence. Strong BPDE excimer fluorescence is observed in the alternating poly(dGdC).poly(dGdC) sequence, whereas it is weak in the homopolymeric poly(dG).poly(dC) and in calf thymus DNA. No excimer fluorescence is observed for the BPDE adducts in poly(dAdC).poly(dGdT) or poly(dAdG).poly(dCdT). It is concluded that the formation of BPDE excimers in polynucleotides requires binding to guanines on different strands on consecutive basepairs. The experimental results are supported by graphics modeling and energy minimization of BPDE adducts in various oligonucleotide sequences. The results show that the most favorable arrangement for excimer formation of the BPDE-dG adducts is in a 5'(dCdG-BPDE).5'(dCdG-BPDE) sequence, where the pyrenyl chromophores interact in the minor groove.
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| 28. |
- Fernandes-Cerqueira, C, et al.
(författare)
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Patients with anti-Jo1 antibodies display a characteristic IgG Fc-glycan profile which is further enhanced in anti-Jo1 autoantibodies
- 2018
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1, s. 17958-
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Tidskriftsartikel (refereegranskat)abstract
- IgG Fc-glycans affect IgG function and are altered in autoimmune diseases and autoantibodies. Anti-histidyl tRNA synthetase autoantibodies (anti-Jo1) are frequent in patients with idiopathic inflammatory myopathies (IIM) and anti-synthetase syndrome (ASS) with associated interstitial lung disease (ILD). Thus, we hypothesized that the total-IgG Fc-glycans from Jo1+ versus Jo1− patients and anti-Jo1-IgG would show characteristic differences, and that particular Fc-glycan features would be associated with specific clinical manifestations. By proteomics based mass spectrometry we observed a high abundance of agalactosylated IgG1 Fc-glycans in ASS/IIM patients (n = 44) compared to healthy age matched controls (n = 24). Using intra-individual normalization of the main agalactosylated glycan (FA2) of IgG1 vs FA2-IgG2, ASS/IIM and controls were distinguished with an area under the curve (AUC) of 79 ± 6%. For Jo1+ patients (n = 19) the AUCs went up to 88 ± 6%. Bisected and afucosylated Fc-glycans were significantly lower in Jo1+ compared to Jo1− patients. Anti-Jo1-IgG enriched from eleven patients contained even significantly lower abundances of bisected, afucosylated and galactosylated forms compared to matched total-IgG. ASS and ILD diagnosis, as well as lysozyme and thrombospondin correlated with Jo1+ characteristic Fc-glycan features. These results suggest that the anti-Jo1+ patient Fc-glycan profile contains phenotype specific features which may underlie the pathogenic role of Jo1 autoantibodies.
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| 31. |
- Graslund, S., et al.
(författare)
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Single-vector three-frame expression systems for affinity-tagged proteins
- 2002
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 215:1, s. 139-147
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Tidskriftsartikel (refereegranskat)abstract
- An effort is presented to create expression vectors which would allow expression of an inserted gene fragment in three reading frames in a single vector from a single promoter but with three separate ribosome binding sites (RBS). Each expression frame would generate an in-frame fusion with an affinity tag to allow efficient recovery of the produced fusion proteins. In the first generation vector, three identical polyhistidyl tags (His(6)) were used as affinity tags for the three expression frames. In the second generation vector, three different tags, an albumin binding domain derived from streptococcal protein G, an IgG binding Staphylococcus aureus protein A-derived domain (Z) and a His(6) tag, were employed to allow frame-specific affinity recovery. To evaluate the systems, model genes have been inserted in three different frames in both vectors. The first vector was demonstrated to produce fusion proteins in all three frames, whereas for the second, with a much wider spacing between the RBSs and affinity tags, expression could only be demonstrated from the first two translational start sites. For both systems, the first translation start was found to be significantly favored over the others. Nevertheless, we believe that the presented results represent the first successful attempt to create single-vector three-frame expression systems, a concept that could become valuable in future combined cloning-expression vectors.
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| 32. |
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| 33. |
- Jorgensen, P. M., et al.
(författare)
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Characterisation of the human APC1, the largest subunit of the anaphase-promoting complex
- 2001
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Ingår i: Gene. - 0378-1119 .- 1879-0038. ; 262:02-jan, s. 51-59
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Tidskriftsartikel (refereegranskat)abstract
- Accurate segregation of sister chromatids during mitosis is necessary to avoid the aneuploidy found in many cancers. The spindle checkpoint, which monitors the metaphase to anaphase transition, has been shown to be defective in cancers with chromosomal instability. This checkpoint regulates the anaphase-promoting complex or cyclosome (APC/C), a cell cycle ubiquitin ligase regulating among other things sister chromatid separation. We have previously investigated the mouse Apc1 protein (previously also called Tsg24), the largest subunit of the APC/C. We have now sequenced a full-length human APC1 cDNA, mapped its chromosomal location, and analysed its intron-exon boundaries. We have also investigated the RNA and protein expression of the Apc1 and other APC/C components in normal and cancer cells and the relative occurrence of expressed sequence tugs (ESTs) representing APC subunits from different tissues. The different APC/C subunits are expressed in most tissues and cell types at fairly constant levels relative to each other, suggesting that they perform their functions as part of a complex. A difference from this pattern is however seen for the APC6, which in some cases is more strongly expressed, suggesting a special function for this protein in certain tissues and cell types.
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| 36. |
- Larsson, M., et al.
(författare)
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High-throughput protein expression of cDNA products as a tool in functional genomics
- 2000
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Ingår i: Journal of Biotechnology. - 0168-1656 .- 1873-4863. ; 80:2, s. 143-157
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Tidskriftsartikel (refereegranskat)abstract
- A proteomics approach has been developed aimed to allow high throughput analysis of protein products expressed from cDNA fragments (expressed sequence tags, ESTs). The concept relies on expression of gene products to generate specific antibodies for protein analysis, such as immunolocalization of the proteins on cellular and subcellular level. To evaluate the system, 55 cDNA clones with predominantly unknown function were selected from a mouse testis cDNA-library. A bacterial expression system was designed that allowed robust expression and easy purification. Protein levels between 15 and 80 mg l(-1) were obtained for 49 of the clones. Five clones were selected for immunization and all yielded functional antibodies that gave specific staining in Western blot screening of samples from various cell types. Furthermore, extensive immunolocalization information on subcellular level was obtained for three of the five clones. All generated data were stored in a relational database, and are made available through a web-interface (http://www.biochem.kth.se/multiscale/), which also provides relevant links and allows homology searches from the original sequences. The possibility to allow analysis of gene products from whole genomes using this 'localization proteomics' approach is discussed.
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| 37. |
- Larsson, M., et al.
(författare)
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The spatial and temporal expression of Tekt1, a mouse tektin C homologue, during spermatogenesis suggest that it is involved in the development of the sperm tail basal body and axoneme
- 2000
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Ingår i: European Journal of Cell Biology. - : Elsevier BV. - 0171-9335 .- 1618-1298. ; 79:10, s. 718-725
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Tidskriftsartikel (refereegranskat)abstract
- Tektins comprise a family of filament-forming proteins that are known to be coassembled with tubulins to form ciliary and flagellar microtubules. Recently we described the sequence of the first mammalian tektin protein, Tekt1 (from mouse testis), which is most homologous with sea urchin tektin C. We have now investigated the temporal and spatial expression of Tekt1 during mouse male germ cell development. By in situ hybridization analysis TEKT1 RNA expression is detected in spermatocytes and in round spermatids in the mouse testis, Immunofluorescence microscopy analysis with anti-Tekt1 antibodies showed no distinct labeling of any subcellular structure in spermatocytes, whereas in round spermatids anti-Tekt1 antibodies co-localize with anti-ANA antibodies to the centrosome. At a later stage, elongating spermatids display a larger area of anti-Tekt1 staining at their caudal ends; as spermiogenesis proceeds, the anti-Tekt1 staining disappears. Together with other evidence, these results provide the first intraspecies evidence that Tekt1 is transiently associated with the centrosome, and indicates that Tekt1 is one of several tektins to participate in the nucleation of the flagellar axoneme of mature spermatozoa, perhaps being required to assemble the basal body.
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| 38. |
- Leijon, M., et al.
(författare)
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STRUCTURAL CHARACTERIZATION OF PNA-DNA DUPLEXES BY NMR - EVIDENCE FOR DNA IN A B-LIKE CONFORMATION
- 1994
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 1520-4995 .- 0006-2960. ; 33:33, s. 9820-9825
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Tidskriftsartikel (refereegranskat)abstract
- The nucleic acid analogues PNA (peptide nucleic acids) hybridize with DNA of complementary sequence. The solution structures of two PNA-DNA duplexes, H-(GCTATGTC)-NH2.d(GACATAGC) and H-(GTAGATCACT)-NH2.d(AGTGATCTAC), have been studied by H-1 NMR. It was found that the PNA-DNA hybrids are base paired by hydrogen bonds, most likely of the Watson-Crick type. From two-dimensional NOESY and COSY results it is concluded that the DNA strand in the PNA-DNA complex adopts a B-like structure with the deoxyribose sugars in the C2'-endo conformation.
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| 39. |
- Lindgren, Joel, et al.
(författare)
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N-terminal engineering of amyloid-beta-binding Affibody molecules yields improved chemical synthesis and higher binding affinity
- 2010
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Ingår i: Protein Science. - : Wiley. - 0961-8368 .- 1469-896X. ; 19:12, s. 2319-2329
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Tidskriftsartikel (refereegranskat)abstract
- The aggregation of amyloid-beta (A beta) peptides is believed to be a major factor in the onset and progression of Alzheimer's disease Molecules binding with high affinity and selectivity to A beta-peptides are important tools for investigating the aggregation process An A beta-binding Affibody molecule, Z(A beta 3), has earlier been selected by phage display and shown to bind A beta(1-40) with nanomolar affinity and to inhibit A beta-peptide aggregation In this study, we create truncated functional versions of the Z(A beta 3) Affibody molecule better suited for chemical synthesis production Engineered Affibody molecules of different length were produced by solid phase peptide synthesis and allowed to form covalently linked homodimers by S-S-bridges The N-terminally truncated Affibody molecules Z(A beta 3)(12-58), Z(A beta 3)(15-58), and Z(A beta 3)(18-58) were produced in considerably higher synthetic yield than the corresponding full-length molecule Z(A beta 3)(1-58) Circular dichroism spectroscopy and surface plasmon resonance-based biosensor analysis showed that the shortest Affibody molecule, Z(A beta 3)(18-58), exhibited complete loss of binding to the A beta(1-40)-peptide, while the Z(A beta 3)(12-58) and Z(A beta 3)(15-58) Affibody molecules both displayed approximately one order of magnitude higher binding affinity to the A beta(1-40)-peptide compared to the full-length Affibody molecule Nuclear magnetic resonance spectroscopy showed that the structure of A beta(1-40) in complex with the truncated Affibody dimers is very similar to the previously published solution structure of the A beta(1-40)-peptide in complex with the full-length Z(A beta 3) Affibody molecule This indicates that the N-terminally truncated Affibody molecules Z(A beta 3)(12-58) and Z(A beta 3)(15-58) are highly promising for further engineering and future use as binding agents to monomeric A beta(1-40)
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| 45. |
- Preger, C., et al.
(författare)
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Characterization of anti-aminoacyl TRNA synthetase autoantibodies in patients with idiopathic inflammatory myopathies
- 2020
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ Publishing Group. - 0003-4967 .- 1468-2060. ; 79, s. 1084-1085
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Idiopathic inflammatory myopathies (IIM) are rare chronic inflammatory diseases associated with high mortality and morbidity [1]. One sub-group of IIM, anti-synthetase syndrome (ASS), is characterized by the presence of autoantibodies that target aminoacyl transfer(t) RNA synthetases (aaRS), together with specific clinical manifestations such as myositis, interstitial lung disease (ILD), arthritis, mechanic’s hand, Raynaud’s syndrome and fever [2]. The most common anti-aaRS autoantibody, anti-Jo1 targeting histidyl tRNA synthetase (HisRS), is present in up to 20-30% of patients with IIM, and up to 90% of patients with myositis and ILD [3, 4]. Besides Jo1, there are today seven other identified autoantigens within the aaRS family.Objectives:A large part of patients with IIM, including individuals with clinical manifestations indicating ASS, test seronegative to all known myositis specific autoantibodies. However, these patients could potentially harbor autoantibodies against targets not tested for in clinic. In this study, we aimed at extending the detection of autoantibodies by including all cytoplasmic aaRS in the analysis of patients with IIM. We hypothesized the existence of new potential autoantigens within this protein family.Methods:The presence of anti-aaRS autoantibodies was determined using a multiplex suspension bead array assay on 242 IIM patients from the Karolinska University Hospital myositis cohort. A panel of 186 recombinant constructs, representing 57 proteins that included full-length or partial sequence overlaps between constructs of all cytoplasmic aaRS as well as other myositis related proteins, were coupled to magnetic color-coded beads and each plasma sample was tested against the complete antigen panel.Results:By the use of this multiplex method we identified patients with autoantibodies against many of the tested aaRS. Autoantibodies binding to HisRS have previously been shown to bind with higher reactivity to the WHEP domain of HisRS and this was also confirmed in this study. We confirmed reactivity against three of the other aaRS tested for in the clinic (PL-12, PL-7, and EJ). In addition, we identified patients positive for anti-Zo, -KS and -HA, autoantibodies usually not screened for in routine. Finally, our data indicates that there are autoantibodies binding to other aaRS than the previously known eight autoantigens, which will be presented.Conclusion:In this study, we could detect autoantibodies in plasma from patients with IIM, both against the most common aaRS autoantigens, but also against other aaRS that are usually not tested for in clinic. We conclude that it is important to continue the studies of anti-aaRS autoantibodies, and their correlation to clinical manifestations, and in the long run also include more aaRS autoantigens in clinical practice.References:[1]Dobloug, G.C., et al., Mortality in idiopathic inflammatory myopathy: results from a Swedish nationwide population-based cohort study. Ann Rheum Dis, 2018. 77(1): p. 40-47.[2]Barsotti, S. and I.E. Lundberg, Myositis an evolving spectrum of disease. Immunol Med, 2018. 41(2): p. 46-54.[3]Vencovsky, J., H. Alexanderson, and I.E. Lundberg, Idiopathic Inflammatory Myopathies. Rheum Dis Clin North Am, 2019. 45(4): p. 569-581.[4]Richards, T.J., et al., Characterization and peripheral blood biomarker assessment of anti-Jo-1 antibody-positive interstitial lung disease. Arthritis Rheum, 2009. 60(7): p. 2183-92.Disclosure of Interests:Charlotta Preger: None declared, Antonella Notarnicola: None declared, Cecilia Hellström: None declared, Edvard Wigren: None declared, Catia Cerqueira: None declared, Peter Nilsson: None declared, Ingrid E. Lundberg Grant/research support from: Bristol Meyer Squibb, Corbus Pharmaceuticals, Inc and Astra Zeneca, Helena Persson: None declared, Susanne Gräslund: None declared, Per-Johan Jakobsson Shareholder of: Gesynta Pharma, Grant/research support from: Gesynta Pharma, AstraZeneca,
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| 50. |
- Tomac, S., et al.
(författare)
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Ionic effects on the stability and conformation of peptide nucleic acid complexes
- 1996
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 118:24, s. 5544-5552
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Tidskriftsartikel (refereegranskat)abstract
- Peptide nucleic acid (PNA) is a DNA analogue in which the negatively charged sugar phosphate backbone has been substituted by uncharged N-(2-aminoethyl)glycine units. The study of a PNA-DNA duplex and the corresponding DNA-DNA duplex gives a unique opportunity to compare two polyelectrolytes with virtually identical geometry but greatly different linear charge density. The results provide a basis for a study of the applicability of the Poisson-Boltzmann (PB) and counterion condensation (CC) theories. UV and circular dichroism spectroscopy as well as isothermal titration calorimetry (ITC) have been used to study the effect of different ions on the stability and conformation of PNA-DNA, PNA-PNA, and DNA-DNA duplexes having the same base sequences. Cations in general destabilize both antiparallel (N/3') and parallel (N/5') PNA-DNA duplexes whereas they stabilize the DNA-DNA duplex. Studies on the effect of monovalent salt such as NaCl on T-m were carried out over a wide range of salt concentrations (0.01 to 5 M). The decrease in the T-m of the N/3' PNA-DNA duplex with increasing ionic strength in the range of concentrations of 0.01 to 0.5 M, where electrostatic effects predominate, is explained in terms of counterion release upon duplex formation in contrast to the counterion association accompanying the formation of a DNA duplex. The uncharged PNA-PNA duplex shows no significant destabilization in this concentration range. The higher stability of the N/3' PNA-DNA compared to the DNA-DNA duplex (Delta Delta G similar to-7 kcal/mol) is ascribed to more favorable entropic contributions consistent with the counterion release that accompanies the PNA-DNA duplex formation. At high salt concentration (>1 M), where electrostatic contributions saturate, similar trends in the decrease in T-m, were observed for the three types of duplexes irrespective of their backbone charges. The destabilizing effects of a series of Na salts with various monovalent anions on N/3' PNA-DNA and PNA-PNA duplexes were found to follow the Hofmeister series, emphasizing the importance of the hydrophobic interaction between nucleobases for the stability of the PNA complexes in high salt concentration.
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