| 1. |
- Ek, Patrik, et al.
(författare)
-
Electrospray Ionization from an Adjustable Gap between two Silicon Chips
- 2009
-
Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 44:2, s. 171-181
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a silicon chip - based electrospray emitter with a variable orifice size is presented. The device consists of two chips, with a thin beam elevating from the center of each of the chips. The chips are individually mounted to form an open gap of a narrow, uniform width between the top areas of the beams. The electrospray is generated at the endpoint of the gap, where the spray point is formed by the very sharp intersection between the crystal planes of the < 100 > silicon chips. Sample solution is applied to the rear end of the gap from a capillary via a liquid bridge, and capillary forces ensure a spontaneous imbibition of the gap. The sample solution is confined to the gap by means of a hydrophobic treatment of the surfaces surrounding the gap, as well as the geometrical boundaries formed by the edges of the gap walls. The gap width could be adjusted between 1 and 25 μm during electrospray experiments without suffering from any interruption of the electrospray process. Using a peptide sample solution, a shift toward higher charge states and increased signal-to-noise ratios was observed when the gap width was decreased. The limit of detection for the peptide insulin (chain B, oxidized) was approximately 4 nM. We also show a successful interfacing of the electrospray setup with capillary electrophoresis.
|
|
| 2. |
- Hartmann, Michael, et al.
(författare)
-
Non-contact protein microarray fabrication using a procedure based on liquid bridge formation
- 2009
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 393:2, s. 591-598
-
Tidskriftsartikel (refereegranskat)abstract
- Contemporary microarrayers of contact or noncontact format used in protein microarray fabrication still suffer from a number of problems, e. g. generation of satellite spots, inhomogeneous spots, misplaced or even absent spots, and sample carryover. In this paper, a new concept of non-contact sample deposition that reduces such problems is introduced. To show the potential and robustness of this pressure-assisted deposition technique, different sample solutions known to cause severe problems or to be even impossible to print with conventional microarrayers were accurately printed. The samples included 200 mg mL(-1) human serum albumin, highly concentrated sticky cell adhesion proteins, pure high-salt cell-lysis buffer, pure DMSO, and a suspension of 5-mu m polystyrene beads. Additionally, a water-immiscible liquid fluorocarbon, which was shown not to affect the functionality of the capture molecules, was employed as a lid to reduce evaporation during microarray printing. The fluorocarbon liquid lid was shown to circumvent hydrolysis of water-sensitive activated surfaces during long-term deposition procedures.
|
|
| 3. |
- Abrahamsson, Johan, et al.
(författare)
-
Complete metabolic response with [18F]fluorodeoxyglucose-positron emission tomography/computed tomography predicts survival following induction chemotherapy and radical cystectomy in clinically lymph node positive bladder cancer
- 2022
-
Ingår i: BJU International. - : Wiley. - 1464-4096 .- 1464-410X. ; 129:2, s. 174-181
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: To determine whether repeated [18F]fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET-CT) scans can predict increased cancer-specific survival (CSS) after induction chemotherapy followed by radical cystectomy (RC). Patients and Methods: Between 2007 and 2018, 86 patients with clinically lymph node (LN)-positive bladder cancer (T1–T4, N1–N3, M0–M1a) were included and underwent a repeated FDG-PET-CT during cisplatin-based induction chemotherapy. The 71 patients that had a response to chemotherapy underwent RC. Response to chemotherapy was evaluated in LNs through repeated FDG-PET-CT and stratified as partial response or complete response using three different methods: maximum standardised uptake value (SUVmax), adapted Deauville criteria, and total lesion glycolysis (TLG). Progression-free survival (PFS) and CSS were analysed for all three methods by Cox regression analysis. Results: After a median follow-up of 40 months, 15 of the 71 patients who underwent RC had died from bladder cancer. Using SUVmax and the adapted Deauville criteria, multivariable Cox regression analyses adjusting for age, clinical tumour stage and LN stage showed that complete response was associated with increased PFS (hazard ratio [HR] 3.42, 95% confidence interval [CI] 1.20–9.77) and CSS (HR 3.30, 95% CI 1.02–10.65). Using TLG, a complete response was also associated with increased PFS (HR 5.17, 95% CI 1.90–14.04) and CSS (HR 6.32, 95% CI 2.06–19.41). Conclusions: Complete metabolic response with FDG-PET-CT predicts survival after induction chemotherapy followed by RC in patients with LN-positive bladder cancer and comprises a novel tool in evaluating response to chemotherapy before surgery. This strategy has the potential to tailor treatment in individual patients by identifying significant response to chemotherapy, which motivates the administration of a full course of induction chemotherapy with a higher threshold for suspending treatment due to toxicity and side-effects.
|
|
| 4. |
- Andersson, Mats, et al.
(författare)
-
Road Friction Estimation
- 2007
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This project is part of the Swedish IVSS program. The aim of IVSS is to stimulate research and development for the road safety of the future. Road conditions with low friction have been identified as a frequent cause of traffic accidents. Therefore, technology to automaticallydetect changes in road conditions and alert the driver or take proper actions with active driver support systems would be a key contribution to increased road safety.The aim of this project was to investigate the possibilities to estimate the tire to road friction.Three different approaches have been developed and evaluated, from concept to early prototypes in test vehicles. In the first method, the estimation of the coefficient of friction is based on the forces and torques that are produced at the front tires at cornering maneuvers.The second method is based on a physical model of the tire behavior and estimates road friction from information on the forces that are produced at straight driving. The third method is based on an optical sensor that classifies the road surface ahead of the vehicle.The three methods have been successfully evaluated in proving ground and public road tests in summer and winter conditions with different tires, and have been compared with reference measurements. The conclusion is that all three methods can be used for tire to road frictionestimation and are recommended for further development and industrialization.
|
|
| 5. |
- Ek, Patrik, et al.
(författare)
-
Electrospray Ionization from a Gap with Adjustable Width
- 2006
-
Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 20:21, s. 3176-3182
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a new concept for electrospray ionization mass spectrometry, where the sample is applied in a gap which is formed between the edges of two triangular-shaped tips. The size of the spray orifice can be changed by varying the gap width. The tips were fabricated from polyethylene terephthalate film with a thickness of 36 μm. To improve the wetting of the gap and sample confinement, the edges of the tips forming the gap were hydrophilized by means of silicon dioxide deposition. Electrospray was performed with gap widths between 1 and 36 μm and flow rates down to 75 nL/min. The gap width could be adjusted in situ during the mass spectrometry experiments and nozzle clogging could be managed by simply widening the gap. Using angiotensin I as analyte, the signal-to-noise ratio increased as the gap width was decreased, and a shift towards higher charge states was observed. The detection limit for angiotensin I was in the low nM range.
|
|
| 6. |
- Eppanapelli, Lavan Kumar, 1988-, et al.
(författare)
-
Investigation of snow single scattering properties of snow based on first order Legendre phase function
- 2017
-
Ingår i: Optics and lasers in engineering. - : Elsevier. - 0143-8166 .- 1873-0302. ; 91, s. 151-159
-
Tidskriftsartikel (refereegranskat)abstract
- Angularly resolved bidirectional reflectance measurements were modelled by ap- proximating a first order Legendre expanded phase function to retrieve single scattering properties of snow. The measurements from 10 different snow types with known density and specific surface area (SSA) were investigated. A near infrared (NIR) spectrometer was used to measure reflected light above the snow surface over the hemisphere in the wavelength region 900 nm to 1650 nm. A solver based on discrete ordinate radiative transfer (DISORT) model was used to retrieve the estimated Legendre coefficients of the phase function and a cor- relation between the coefficients and physical properties of different snow types is investigated. Results of this study suggest that the first two coefficients of the first order Legendre phase function provide sufficient information about the physical properties of snow where the latter captures the anisotropic behaviour of snow and the former provides a relative estimate of the single scattering albedo of snow. The coefficients of the first order phase function were com- pared with the experimental data and observed that both the coefficients are in good agreement with the experimental data. These findings suggest that our approach can be applied as a qualitative tool to investigate physical properties of snow and also to classify different snow types.
|
|
| 7. |
- Hamberg, Anders, et al.
(författare)
-
C-terminal ladder sequencing of peptides using an alternative nucleophile in carboxypeptidase Y digests
- 2006
-
Ingår i: Analytical Biochemistry. - : Elsevier BV. - 0003-2697 .- 1096-0309. ; 357:2, s. 167-172
-
Tidskriftsartikel (refereegranskat)abstract
- A method for improved sequence coverage in C-terminal sequencing of peptides, based on carboxypeptidase digestion, is described. In conventional carboxypeptidase digestions, the peptide substrate is usually extensively degraded and a full amino acid sequence cannot be obtained due to the lack of a complete peptide ladder. In the presented method, a protecting group is introduced at the C terminus of a fraction of the peptide fragments formed in the digest, and thereby further degradation of the C-terminally modified peptides are slowed down. The protecting group was attached to the C-terminal amino acid through a carboxypeptidase-catalyzed reaction with an alternative nucleophile, 2-pyridylmethylamine, added to the aqueous digestion buffer. Six peptides were digested by carboxypeptidase Y with and without 2-pyridylmethylamine present in the digest buffer, and the resulting fragments subsequently were analyzed with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Comparison of the two digestion methods showed that the probability of successful ladder sequencing increased, by more than 50% using 2-pyridylmethylamine as a competing nucleophile in carboxypeptidase Y digests.
|
|
| 8. |
- Kempka, Martin, et al.
(författare)
-
Improved method for peak picking in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
- 2004
-
Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 18:11, s. 1208-1212
-
Tidskriftsartikel (refereegranskat)abstract
- A method for peak picking for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is described. The method is based on the assumption that two sets of ions are formed during the ionization stage, which have Gaussian distributions but different velocity profiles. This gives rise to a certain degree of peak skewness. Our algorithm deconvolutes the peak and utilizes the fast velocity, bulk ion distribution for peak picking. Evaluation of the performance of the new method was conducted using peptide peaks from a bovine serum albumin (BSA) digest, and compared with the commercial peak-picking algorithms Centroid and SNAP. When using the new two-Gaussian algorithm, for strong signals the mass accuracy was equal to or marginally better than the results obtained from the commercial algorithms. However, for weak, distorted peaks, considerable improvement in both mass accuracy and precision was obtained. This improvement should be particularly useful in proteomics, where a lack of signal strength is often encountered when dealing with weakly expressed proteins. Finally, since the new peak-picking method uses information from the entire signal, no adjustments of parameters related to peak height have to be made, which simplifies its practical use.
|
|
| 9. |
- Sjödahl, Johan, et al.
(författare)
-
Chip with twin anchors for reduced ion suppression and improved mass accuracy in MALDI-TOF mass spectrometry
- 2005
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 77:3, s. 827-832
-
Tidskriftsartikel (refereegranskat)abstract
- A new sample target for matrix-assisted laser desorption/ionization mass spectrometry is described. The target consists of pairs of elevated hydrophilic anchor surfaces, positioned in proximity onto a microchip. The anchors are used to obtain separate preparations of sample and external standard, while both anchor surfaces are irradiated simultaneously by the laser pulse. Using a standard, based on six peptides, a 2-fold improvement in mass accuracy is observed. Also, ion suppression is significantly reduced. With a one peptide calibration standard, 22 tryptic fragments from a BSA digest are detected using the twin-anchor concept, whereas only 14 fragments are detected when the sample and standard are laser-ablated as a mixture from a conventional anchor target. A volume of similar to30 pL of sample solution of angiotensin I is transferred to the anchor surface, under a thin layer of a perfluorocarbon, to prevent a concentration bias due to evaporation. With this arrangement, a detection limit of 1.5 amol was achieved with a signal-to-noise ratio of 22:1.
|
|
| 10. |
- Villanueva, Walter, et al.
(författare)
-
Microdroplet deposition under a liquid medium
- 2007
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 23:3, s. 1171-1177
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental and numerical study of the factors affecting the reproducibility of microdroplet depositions performed under a liquid medium is presented. In the deposition procedure, sample solution is dispensed from the end of a capillary by the aid of a pressure pulse onto a substrate with pillar-shaped sample anchors. The deposition was modeled using the convective Cahn-Hilliard equation coupled with the Navier-Stokes equations with added surface tension and gravity forces. To avoid a severe time-step restriction imposed by the fourth-order Cahn-Hilliard equation, a semi-implicit scheme was developed. An axisymmetric model was used, and an adaptive finite element method was implemented. In both the experimental and numerical study it was shown that the deposited volume mainly depends on the capillary-substrate distance and the anchor surface wettability. A critical equilibrium contact angle has been identified below which reproducible depositions are facilitated.
|
|
