| 1. |
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| 2. |
- Aronsson, Göran, et al.
(författare)
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Remarkably slow folding of a small protein.
- 1997
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Ingår i: FEBS Letters. - 0014-5793 .- 1873-3468. ; 411:2-3, s. 359-364
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Tidskriftsartikel (refereegranskat)abstract
- Equilibrium denaturation of the 72 amino acid alpha/beta-protein MerP, by acid, guanidine hydrochloride, or temperature, is fully reversible and follows a two-state model in which only the native and unfolded states are populated. A cis-trans equilibrium around a proline peptide bond causes a heterogeneity of the unfolded state and gives rise to a slow- and a fast folding population. With a rate constant of 1.2 s(-1) for the major fast folding population, which has none of the common intrinsically slow steps, MerP is the slowest folding protein of this small size yet reported.
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| 3. |
- Berglund, Anders, et al.
(författare)
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The equilibrium unfolding of MerP characterized by multivariate analysis of 2D NMR data
- 2005
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Ingår i: Journal of magnetic resonance. - San Diego : Academic Press. - 1090-7807 .- 1096-0856. ; 172:1, s. 24-30
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Tidskriftsartikel (refereegranskat)abstract
- A general problem when analysing NMR spectra that reflect variations in the environment of target molecules is that different resonances are affected to various extents. Often a few resonances that display the largest frequency changes are selected as probes to reflect the examined variation, especially in the case, where the NMR spectra contain numerous resonances. Such a selection is dependent on more or less intuitive judgements and relying on the observed spectral variation being primarily caused by changes in the NMR sample. Second, recording changes observed for a few (albeit significant) resonances is inevitably accompanied by not using all available information in the analysis. Likewise, the commonly used chemical shift mapping (CSM) [Biochemistry 39 (2000) 26, Biochemistry 39 (2000) 12595] constitutes a loss of information since the total variation in the data is not retained in the projection into this single variable. Here, we describe a method for subjecting 2D NMR time-domain data to multivariate analysis and illustrate it with an analysis of multiple NNIR experiments recorded at various folding conditions for the protein MerP. The calculated principal components provide an unbiased model of variations in the NNIR spectra and they can consequently be processed as NMR data, and all the changes as reflected in the principal components are thereby made available for visual inspection in one single NMR spectrum. This approach is much less laborious than consideration of large numbers of individual spectra, and it greatly increases the interpretative power of the analysis.
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| 4. |
- Brorsson, Ann-Christin, et al.
(författare)
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GuHCl and NaCl-dependent hydrogen exchange in MerP reveals a well-defined core with an unusual exchange pattern
- 2006
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 357:5, s. 1634-1646
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Tidskriftsartikel (refereegranskat)abstract
- We have analysed hydrogen exchange at amide groups to characterise the energy landscape of the 72 amino acid residue protein MerP. From the guanidine hydrochloride (GuHCl) dependence of exchange in the pre-transitional region we have determined free energy values of exchange (ΔGHX) and corresponding m-values for individual amide protons. Detailed analysis of the exchange patterns indicates that for one set of amide protons there is a weak dependence on denaturant, indicating that the exchange is dominated by local fluctuations. For another set of amide protons a linear, but much stronger, denaturant dependence is observed. Notably, the plots of free energy of exchange versus [GuHCl] for 16 amide protons show pronounced upward curvature, and a close inspection of the structure shows that these residues form a well-defined core in the protein. The hydrogen exchange that was measured at various concentrations of NaCl shows an apparent selective stabilisation of this core. Detailed analysis of this exchange pattern indicates that it may originate from selective destabilisation of the unfolded state by guanidinium ions and/or selective stabilisation of the core in the native state by chloride ions. © 2006 Elsevier Ltd. All rights reserved.
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| 5. |
- Brorsson, Ann-Christin, 1969-
(författare)
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The Folding Energy Landscape of MerP
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is based on studies, described in four papers, in which the folding energy landscape of MerP was investigated by various techniques. MerP is a water-soluble 72 amino acid protein with a secondary structure consisting of four anti-parallel β-strands and two α-helices on one side of the sheet in the order β1α1β2β3α2β4.The first paper describes the use of CD and fluorescence analysis to examine the folding/unfolding process of MerP. From these experiments it was found that the protein folds according to a two-state model in which only the native and unfolded forms are populated without any visible intermediates. With a rate constant of 1.2 s-1, the folding rate was found to be unusually slow for a protein of this size.The studies presented in the second and third papers were based on measurements of native-state amide proton exchange at different temperatures (Paper II) and GuHCl concentrations (Paper III) in the pre-transitional region. In these studies partially unfolded forms were found for MerP which are essentially unrelated to each other. Thus, in the folding energy landscape of MerP, several intermediates seem to occur on different folding trajectories that are parallel to each other. The slow folding rate of MerP might be coupled to extensive visitation of these conformations. Hydrogen exchange in MerP did also reveal structure-dependent differences in compactness between the denatured states in GuHCl and H2O.In the last paper multivariate data analysis was applied to 2-dimensional NMR data to detect conformational changes in the structure of MerP induced by GuHCl. From this analysis it was suggested that regions involved in the most flexible part of the protein structure are disrupted at rather low denaturant concentrations (< 2.1 M GuHCl) while the native structures of the most stable parts are still not completely ruptured at 2.9 M GuHCl.Finally, the stability, kinetics, contact order and folding nuclei of six proteins with similar topology (MerP, U1A, S6, ADA2h, AcP and HPr) were compared. In this analysis it was found that their folding properties are quite diverse, despite their topological similarities, and no general rules that have been formulated yet can adequately predict their folding behaviour.
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| 6. |
- Brorsson, Ann-Christin, et al.
(författare)
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The “Two-State folder” MerP forms partially unfolded structures that show temperature dependent hydrogen exchange
- 2004
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Ingår i: Journal of Molecular Biology. - London : Academic Press. - 0022-2836 .- 1089-8638. ; 340:2, s. 333-344
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Tidskriftsartikel (refereegranskat)abstract
- We have analysed the folding energy landscape of the 72 amino acid protein MerP by monitoring native state hydrogen exchange as a function of temperature in the range of 7-55 degrees C. The temperature dependence of the hydrogen exchange has allowed us to determine DeltaG, DeltaH and DeltaC(p) values for the conformational processes that permit hydrogen exchange. When studied with the traditional probes, fluorescence and CD, MerP appears to behave as a typical two-state protein, but the results from the hydrogen exchange analysis reveal a much more complex energy landscape. Analysis at the individual amino acid level show that exchange is allowed from an ensemble of partially unfolded structures (i.e. intermediates) in which the stabilities at the amino acid level form a broad distribution throughout the protein. The formation of partially unfolded structures might contribute to the unusually slow folding of MerP.
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| 7. |
- Brorsson, Annelie, 1963, et al.
(författare)
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Development and evaluation of a new seated heel-rise test in the early stages of rehabilitation after an acute Achilles tendon rupture.
- 2014
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Ingår i: 16th ESSKA (European Society of Sports Traumatology, Knee Surgery and Arthroscopy) Congress, 14-17 May 2014, Amsterdam, Netherlands.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The early stages of rehabilitation appear to be of great importance for outcome after an Achilles tendon rupture. It is a challenge to evaluate the patients’ calf muscle endurance at this stage in a safe and adequate way. The aim of our study was to develop a seated heel-rise test suitable for evaluating calf muscle endurance three months after an Achilles tendon rupture. Furthermore we wanted to evaluate how the seated heel-rise test correlated to the ability to perform one-legged standing heel-rise and patient-reported symptoms. Method: Ninety-three patients, 79 men and 14 women, mean age of 40 (20-63) years, were included from a cohort of 100 patients participating in a prospective, randomized controlled trial comparing non-surgical and surgical treatment after Achilles tendon rupture. Forty-seven were treated with surgery and 46 with non-surgery. They were evaluated after 3, 6 and 12 months. Patient reported outcome was evaluated with Achilles Tendon Rupture Score (ATRS) and functional outcome with seated and standing heel-rise test. The seated heel-rise test was performed with the patient sitting with hip and knee in 90°. A leg extension weight-training machine was used to provide load onto the patient’s thigh at 50% body weight. The limb symmetry index (LSI=injured/healthy x 100) was calculated in order to compare the results from the seated and standing heel-rise test. Results: Ninety-one patients out of 93 (98%) could perform the seated heel-rise test. At the 3-month follow-up there was a significant difference (p<0.01) in the seated heel-rise test between the injured and the healthy side. There were no significant differences between the surgical and non-surgical treatment groups. There were significant differences in the seated heel-rise test and in ATRS (p<0.01) when comparing the group who could perform a standing heel-rise test at the 3-months follow-up, with the group who could not. There were significant correlations between the LSI-values in the seated heel-rise height at the 3-month follow-up and the standing heel-rise height at the 6-month (r=0.36, p<0.001, n= 91) and the 12-month follow-up (r=0.35, p=0.001, n=85). There were also significant correlations (r=0.22-0.37, p=<0.04) between the seated heel-rise test and ATRS. Conclusions: The seated heel-rise-test has the capacity to identify differences between the injured and the healthy side three months after injury. This test also correlates with patient reported outcomes and the heel-rise ability at 6 and 12 months. This test appears to be a safe and suitable test for evaluating calf muscle endurance and function in the early stages of rehabilitation after an Achilles tendon rupture.
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| 8. |
- Brorsson, Annelie, 1963, et al.
(författare)
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Long-term follow up after acute Achilles tendon rupture.
- 2015
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Ingår i: Danish Sports Medicine Congress, Copenhagen, January 22-24, 2015. - : Danish Association of Sports Medicine.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- It is still unknown why many patients never fully recover after an Achilles tendon rupture (ATR). The aim of this study was to perform a long-term follow-up (5-9 years) of patients treated either surgically or non-surgically after an ATR. Furthermore, we wanted to examine if the patients had a tendon elongation on the injured side and evaluate if this correlated to function, symptoms and foot structure. Material and Method Sixty-seven patients (13 women) mean age of 50 years were evaluated 5-9 years after injury. Thirty-five patients were treated with surgery and 32 with non-surgery. Patient reported outcome and activity level, lower leg function, tendon length, and foot-structure were evaluated. Both the healthy and the injured side were examined and the limb symmetry index (LSI=injured/healthy x 100) was calculated. Results There were significant differences between the healthy and injured side in all function tests (p<0.001-0.015) and the tendon was significantly longer on the injured side (p<0.001) independent of treatment. There were no significant correlations between tendon length and patient reported outcome, function or foot structure. The heel-rise height increased significantly (p<0.000) from the 1 year- to the 5-9-years-follow up. The mean Achilles tendon Total Rupture Score (ATRS) was 91/100, indicating minor symptoms. Conclusion: Patients with an Achilles tendon rupture continues to have significant deficits in tendon structure and function 5-9 years after injury. There is, however continued improvement between the 1 and 5-9 year follow-up.
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| 9. |
- Brorsson, Annelie, 1963, et al.
(författare)
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Recovery of calf muscle endurance 3 months after an Achilles tendon rupture.
- 2016
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Ingår i: Scandinavian journal of medicine & science in sports. - : Wiley. - 1600-0838 .- 0905-7188. ; 26:7, s. 844-853
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to evaluate calf muscle endurance in a seated position 3 months after an Achilles tendon rupture and to evaluate how the ability to perform standardized seated heel-rises correlated to the single-leg standing heel-rise test and to patient-reported symptoms evaluated with the Achilles tendon Total Rupture Score (ATRS) 3 and 6 months after the injury. Ninety-three patients were included from a cohort of 101 patients participating in a prospective, randomized controlled trial comparing surgical and nonsurgical treatment after Achilles tendon rupture. Forty-seven patients were treated surgically and 46 nonsurgically. Ninety-one patients out of 93 (98%) could perform the standardized seated heel-rises. At the 3-month follow-up, there was a significant difference (P<0.001) between the injured and the healthy side performing standardized seated heel-rises. There were also significant correlations (r=0.29-0.37, P=<0.05) between the standardized seated heel-rises and ATRS 3 and 6 months after injury in the group who could not perform single-leg standing heel-rises. There were no significant differences between the surgical and nonsurgical treatment groups. The evaluation of standardized seated heel-rises appears to be a useful tool to quantify progress and predict future functional performance and patient-reported symptoms.
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| 10. |
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