| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Morin Zetterberg, Malin, et al.
(författare)
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Optimization of lipodisk properties by modification of the extent and density of the PEG corona
- 2016
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 484, s. 86-96
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Tidskriftsartikel (refereegranskat)abstract
- Lipodisks are nanosized flat, circular, phospholipid bilayers that are edge-stabilized by polyethylene glycol-conjugated lipids (PEG-lipids). Over the last decade, lipodisks stabilized with PEG of molecular weight 2000 or 5000 have been shown to hold high potential as both biomimetic membranes and drug carriers. In this study we investigate the possibilities to optimize the properties of the lipodisks, and widen their applicability, by reducing the PEG molecular weight and/or the density of the PEG corona. Results obtained by cryo-transmission electron microscopy and dynamic light scattering show that stable, well-defined lipodisks can be produced from mixtures of distearoylphosphatidylcholine (DSPC) and distearoylphosphatidylethanolamine conjugated to PEG of molecular weight 1000 (DSPE-PEG(1000)). Preparations based on the use of DSPE-PEG(750) tend, in contrast, to be polydisperse in size and structure. By comparing immobilization of lipodisks stabilized with DSPE-PEG(1000), DSPE-PEG(2000), and DSPE-PEG(5000) to porous and smooth silica surfaces, we show that the amount of surface bound disks can be considerably improved by the use of PEG-lipids with reduced molecular weight. Further, a modified preparation protocol that enables production of lipodisks with very low PEG-lipid content is described. The reduced PEG density, which facilitates the incorporation of externally added ligand-linked PEG-lipids, is shown to be beneficial for the production of targeting lipodisks.
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| 3. |
- Ahlgren, Bengt, et al.
(författare)
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Content, Connectivity and Cloud: Ingredients for the Network of the Future
- 2011. - 9
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Ingår i: IEEE Communications Magazine. - : IEEE Communications Society. - 0163-6804 .- 1558-1896. ; 49, s. 62-70
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Tidskriftsartikel (refereegranskat)abstract
- A new network architecture for the Internet needs ingredients from three approaches: information-centric networking, cloud computing integrated with networking, and open connectivity. Information-centric networking considers pieces of information as first-class entities of a networking architecture, rather than only indirectly identifying and manipulating them via a node hosting that information; this way, information becomes independent from the devices they are stored in, enabling efficient and application-independent information caching in the network. Cloud networking offers a combination and integration of cloud computing and virtual networking. It is a solution that distributes the benefits of cloud computing more deeply into the network, and provides a tighter integration of virtualisation features at computing and networking levels. To support these concepts, open connectivity services need to provide advanced transport and networking mechanisms, making use of network and path diversity (even leveraging direct optical paths) and encoding techniques, and dealing with ubiquitous mobility of user, content and information objects in a unified way.
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| 4. |
- Ahlgren, Cecilia, 1946, et al.
(författare)
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The effect of live, attenuated measles vaccine and measles infection on measles antibody levels in serum and CSF of patients with multiple sclerosis or clinically isolated syndrome.
- 2011
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Ingår i: Journal of neuroimmunology. - : Elsevier BV. - 1872-8421 .- 0165-5728. ; 235:1-2, s. 98-103
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Tidskriftsartikel (refereegranskat)abstract
- High occurrence of measles, rubella and varicella zoster antibodies has been used as a biomarker for MS (the MRZ test). We analyzed measles antibody titres with respect to measles infection/measles vaccination status in 166 patients with MS or clinically isolated syndrome. Fifty blood donors served as controls. Measles vaccination yielded CSF measles antibodies in fewer patients (62%) than measles infection did (87%, p=0.001) and yielded lower measles titres in both serum and CSF (p<0.001). Controls had lower CSF measles titres than patients with measles vaccination alone (p<0.001). Childhood vaccinations probably reduce the sensitivity of the MRZ diagnostic test for MS.
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| 5. |
- Ahlgren, Per, 1960-, et al.
(författare)
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Research Collaboration between Stockholm University and other Swedish Academic Institutions : A Bibliometric Study to Support Decisions on Library Collaboration
- 2015
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Ingår i: Qualitative and Quantitative Methods in Libraries. - 2241-1925. ; :SI, s. 49-60
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Tidskriftsartikel (refereegranskat)abstract
- Academic libraries collaborate in several ways. For instance, collaboration can concern standards for indexing and statistics, technical solutions or collection development. A question that a given academic library might ask is with which other academic libraries the library should principally collaborate. In this study, we show how bibliometric methods can be used to generate information that can support decision making with regard to the question at stake. We evaluate the amount of research collaboration between Stockholm University and other Swedish academic institutions across five publishing years, and for the whole considered time period, where research collaboration is operationalized as co-publishing. A dataset of publications obtained from Web of Science, where each publication has at least one Stockholm University address, is used in the study. Co-publishing rates, non-fractionalized and fractionalized, across the publishing years and for the whole for period, for Stockholm University and other Swedish academic institutions, are reported. Further, parts of the outcome of the study are visualized in terms of co-publishing networks.
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| 6. |
- Ahlgren, Per, et al.
(författare)
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Research collaboration between Stockholm University and other Swedish academic institutions : a bibliometric study to support decisions on library collaboration
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Ingår i: Qualitative and Quantitative Methods in Libraries. - 2241-1925.
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Tidskriftsartikel (refereegranskat)abstract
- Academic libraries collaborate in several ways. For instance, collaboration can concern standards for indexing and statistics, technical solutions or collection development. A question that a given academic library might ask is with which other academic libraries the library should principally collaborate. In this study, we show how bibliometric methods can be used to generate information that can support decision making with regard to the question at stake. We evaluate the amount of research collaboration between Stockholm University and other Swedish academic institutions across five publishing years, and for the whole considered time period, where research collaboration is operationalized as co-publishing. A dataset of publications obtained from Web of Science, where each publication has at least one Stockholm University address, is used in the study. Co-publishing rates, non-fractionalized and fractionalized, across the publishing years and for the whole for period, for Stockholm University and other Swedish academic institutions, are reported. Further, parts of the outcome of the study are visualized in terms of co-publishing networks.
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| 7. |
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| 8. |
- Ahlgren, Sara, 1979-, et al.
(författare)
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EGF-targeting lipodisks for specific delivery of poorly water-soluble anticancer agents to tumour cells
- 2017
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 7:36, s. 22178-22186
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Tidskriftsartikel (refereegranskat)abstract
- Concerns regarding poor aqueous solubility, high toxicity and lack of specificity impede the translation of many hydrophobic anticancer agents into safe and effective anticancer drugs. The application of colloidal drug delivery systems, and in particular the use of lipid-based nanocarriers, has been identified as a promising means to overcome these issues. PEG-stabilized lipid nanodisks (lipodisks) have lately emerged as a novel type of biocompatible, nontoxic and adaptable drug nanocarrier. In this study we have explored the potential of lipodisks as a platform for formulation and tumour targeted delivery of hydrophobic anticancer agents. Using curcumin as a model compound, we show that lipodisks can be loaded with substantial amounts of hydrophobic drugs (curcumin/lipid molar ratio 0.15). We demonstrate moreover that by deliberate choice of preparation protocols the lipodisks can be provided with relevant amounts of targeting proteins, such as epidermal growth factor (EGF). Data from in vitro cell studies verify that such EGF-decorated curcumin-loaded lipodisks are capable of EGF-receptor specific targeting of human A-431 tumour cells, and strongly suggest that the interaction between the lipodisks and the tumour cells results in receptor-mediated internalization of the disks and their cargo.
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| 9. |
- Ahlgren, Sara, et al.
(författare)
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Evaluation of maleimide derivative of DOTA for site-specific labeling of recombinant affibody molecules
- 2008
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Ingår i: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 19:1, s. 235-243
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Tidskriftsartikel (refereegranskat)abstract
- Affibody molecules are a new class of small (7 kDa) scaffold affinity proteins, which demonstrate promising properties as agents for in vivo radionuclide targeting. The Affibody scaffold is cysteine-free and therefore independent of disulfide bonds. Thus, a single thiol group can be engineered into the protein by introduction of one cysteine. Coupling of thiol-reactive bifunctional chelators can enable site-specific labeling of recombinantly produced Affibody molecules. In this study, the use of 1,4,7,10-tetraazacyclododecane-1,4,7-tris-acetic acid-10-maleimidoethylacetamide (MMA-DOTA) for 111 In-labeling of anti-HER2 Affibody molecules His 6-Z HER2:342-Cys and Z HER2:2395-Cys has been evaluated. The introduction of a cysteine residue did not affect the affinity of the proteins, which was 29 pM for His 6-Z HER2:342-Cys and 27 pM for Z HER2:2395-Cys, comparable with 22 pM for the parental Z HER2:342. MMA-DOTA was conjugated to DTT-reduced Affibody molecules with a coupling efficiency of 93% using a 1:1 molar ratio of chelator to protein. The conjugates were labeled with 111 In to a specific radioactivity of up to 7 GBq/mmol, with preserved binding for the target HER2. In vivo, the non-His-tagged variant 111 In-[MMA-DOTA-Cys61]-Z HER2:2395-Cys demonstrated appreciably lower liver uptake than its His-tag-containing counterpart. In mice bearing HER2-expressing LS174T xenografts, 111 In-[MMA-DOTA-Cys61]-Z HER2:2395-Cys showed specific and rapid tumor localization, and rapid clearance from blood and nonspecific compartments, leading to a tumor-to-blood-ratio of 18 +/- 8 already 1 h p.i. Four hours p.i., the tumor-to-blood ratio was 138 +/- 8. Xenografts were clearly visualized already 1 h p.i.
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| 10. |
- Ahlgren, Sara, et al.
(författare)
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Kit formulation for 99mTc-labeling of recombinant anti-HER2 Affibody molecules with a C-terminally engineered cysteine
- 2010
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Ingår i: Nuclear Medicine and Biology. - : Elsevier BV. - 0969-8051 .- 1872-9614. ; 37:5, s. 539-546
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Molecular imaging of HER2-expression in malignant tumors provides potentially important information for patient management. Affibody molecules have shown to be suitable tracers for imaging applications using SPECT or PET. Results from an earlier evaluation of the application of site specific 99mTc-labeling on the Affibody molecule, ZHER2:2395-C, were favorable. Methods: As a preparation for clinical application of this tracer we have developed and evaluated a robust single-vial freeze-dried kit, allowing labeling of the Affibody molecule, ZHER2:2395-C, with 99mTc. Results: The composition of the kit (containing glucoheptonate, EDTA and tin(II)-chloride), as well as the protein amount and the pertechnetate volume were optimized for a high labeling yield (> 90 %) and minimal presence of reduced hydrolyzed technetium colloids (< 1 %). The specificity to HER2 receptors, the binding competence and the stability in PBS and murine serum were verified in vitro. The shelf-life was also evaluated in vitro, showing no reduction in labeling yield or binding capacity to HER2-expressing cells after over 400 days of storage of the single-vial freeze-dried kit. Conclusions: ZHER2:2395-C labeled with 99mTc using the lyophilized kit was stable and resulted in a favorable biodistribution in an in vivo evaluation in normal NMRI mice.
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