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L H Andersen

Publications and source records attributed to L H Andersen.

At least 19 recordsLinked to original sources
PubMed2006

The gas-phase absorption spectrum of a neutral GFP model chromophore.

We have studied the gas-phase absorption properties of the green fluorescent protein (GFP) chromophore in its neutral (protonated) charge state in a heavy-ion storage ring. To accomplish this we synthesized a new molecular chromophore with a charged NH(3) group attached to a neutral model chromophore of GFP. The gas-phase absorption cross section of this chromophore molecule as a function of the wavelength is compared to the well-known absorption profile of GFP. The chromophore has a maximum absorption at 415 +/- 5 nm. When corrected for the presence of the charged group attached to the GFP model chromophore, the unperturbed neutral chromophore is predicted to have an absorption maximum at 399 nm in vacuum. This is very close to the corresponding absorption peak of the protein at 397 nm. Together with previous data obtained with an anionic GFP model chromophore, the present data show that the absorption of GFP is primarily determined by intrinsic chromophore properties. In other words, there is strong experimental evidence that, in terms of absorption, the conditions in the hydrophobic interior of this protein are very close to those in vacuum.

Animals↗
PubMed2006

S1 and S2 excited States of gas-phase Schiff-base retinal chromophores.

Photoabsorption studies of 11-cis and all-trans Schiff-base retinal chromophore cations in the gas phase have been performed at the electrostatic ion storage ring in Aarhus. A broad absorption band due to the optically allowed excitation to the first electronically excited singlet state (S1) is observed at around 600 nm. A second "dark" excited state (S2) just below 400 nm is reported for the first time. It is located approximately 1.2 eV above S1 for both chromophores. The S2 state was not visible in a solution measurement where only one highly blueshifted absorption band corresponding to the first excited state was visible. Knowledge of the position of the excited states in retinal is essential for the understanding of the fast photoisomerization in, for example, visual pigments.

Gases↗
PubMed2005

Molecular size effect in NCO and NCS dianion resonances.

Cross sections for electron-impact detachment and electron-impact dissociation of NCO- and NCS- were measured from about 3 to about 40 eV. The former are found to follow a classical prediction with a threshold energy of 9.1 +/- 0.1 eV for NCO- and 8.9 +/- 0.2 eV for NCS-. When the incoming electron binds to the monoanion, a short-lived dianion complex is formed, which is revealed as a resonance in the cross section. For NCO- a resonance is evident at 9.3 +/- 0.2 eV, which implies that the dianion lies above the monoanion by this amount of energy. In the case of NCS- two resonances are evident at 8.4 +/- 0.2 and 19.0 +/- 0.5 eV, respectively. The low-energy NCS dianion is less unstable than the dianion of NCO, which in turn is less unstable than the CN dianion (10-eV resonance). Thus the resonance shifts down in energy with the increasing size of the anion, a fact which is attributed to a decrease in Coulomb energy between the spatially separated electrons.

Journal Article↗
PubMed2005

Absorption spectra of photoactive yellow protein chromophores in vacuum.

The absorption spectra of two photoactive yellow protein model chromophores have been measured in vacuum using an electrostatic ion storage ring. The absorption spectrum of the isolated chromophore is an important reference for deducing the influence of the protein environment on the electronic energy levels of the chromophore and separating the intrinsic properties of the chromophore from properties induced by the protein environment. In vacuum the deprotonated trans-thiophenyl-p-coumarate model chromophore has an absorption maximum at 460 nm, whereas the photoactive yellow protein absorbs maximally at 446 nm. The protein environment thus only slightly blue-shifts the absorption. In contrast, the absorption of the model chromophore in aqueous solution is significantly blue-shifted (lambda(max) = 395 nm). A deprotonated trans-p-coumaric acid has also been studied to elucidate the effect of thioester formation and phenol deprotonation. The sum of these two changes on the chromophore induces a red shift both in vacuum and in aqueous solution.

Bacterial Proteins↗
PubMed2005

Tuning the continuum ground state energy of NO2- 2 by water molecules.

Electron scattering on NO-2, NO-2 x (H2O), and NO-2 x (H2O)(2) was performed in two storage rings. We confirm the presence of earlier reported NO2-2 dianion resonances and show that they remain when water is attached. Importantly, hydration tunes the energy: each water molecule lowers the ground state energy by 0.8 +/- 0.3 eV relative to the monoanion. NO2-2 is observed to decay by two-electron emission, possibly in combination with fragmentation. NO(2-)2 x (H2O) mainly decays into NO-2 + H2O + e(-).

Journal Article↗
PubMed2004

Electron scattering on centrosymmetric molecular dianions Pt(CN)4(2-) and Pt(CN)6(2-).

Electron scattering on stored Pt(CN)2-4 and Pt(CN)2-6 centrosymmetric molecular dianions has been performed at the electrostatic storage ring ELISA. The thresholds for production of neutral particles by electron bombardment were found to be 17.2 and 18.7 eV, respectively. The relatively high thresholds reflect the strong Coulomb repulsion in the incoming channel as well as a high energetic stability of the target electrons. A trianion resonance was identified with a positive energy of 17.0 eV for the Pt(CN)2-4 square-planar complex, while three trianion resonances were identified for the Pt(CN)2-6 octahedral complex with positive energies of 15.3, 18.1, and 20.1 eV.

Journal Article↗
PubMed2004

Electron scattering on OH-(H2O)n clusters (n = 0-4).

The cross sections for electron scattering on OH-(H2O)n for n = 0-4 were measured from threshold to approximately 50 eV. All detachment cross sections were found to follow the classical prediction given earlier [Phys. Rev. Lett. 74, 892 (1995)] with a threshold energy for electron-impact detachment that increased upon sequential hydration, yielding values in the range from 4.5 eV +/- 0.2 eV for OH- to 12.10 eV +/- 0.5 eV for OH-(H2O)4. For n > or = 1, we found that approximately 80% of the total reaction events lead to electron detachment plus total dissociation of the clusters into the constituent molecules of OH and H2O. Finally, we observed resonances in the cross sections for OH-(H2O)3 and for OH-(H2O)4. The resonances were located at approximately 15 eV and were ascribed to the formation of dianions in excited states.

Journal Article↗
PubMed2003

Vibrationally resolved photoabsorption spectroscopy of red fluorescent protein chromophore anions.

Photoabsorption studies of red fluorescent protein chromophore anions have been performed at the ELISA electrostatic heavy-ion storage ring. The broad absorption band due to electronic excitation of the chromophores is tuned to a longer wavelength (redshifted) by extending the electronic conjugation of the molecule. A clear vibrational progression is resolved with E(vib) approximately 380 and 520 cm(-1) for two different forms of the chromophore. The vibrational modes correspond to collective motions of the entire molecular structure. It is argued that the excited electronic state has an equilibrium configuration far from that of the electronic ground state, i.e., poor Franck Condon overlap.

Absorption↗
PubMed2001

Absorption spectrum of the green fluorescent protein chromophore anion in vacuo.

A sensitive photoabsorption technique for studies of gas-phase biomolecules has been used at the ELISA electrostatic heavy-ion storage ring. We show that the anion form of the chromophore of the green fluorescent protein in vacuo has an absorption maximum at 479 nm, which coincides with one of the two absorption peaks of the protein. Its absorption characteristics are therefore ascribed to intrinsic chemical properties of the chromophore. Evidently, the special beta-can structure of the protein provides shielding of the chromophore from the surroundings without significantly changing the electronic structure of the chromophore through interactions with amino acid side chains.

Anions↗
PubMed2001

Acute respiratory tract infections and mannose-binding lectin insufficiency during early childhood.

CONTEXT: Hospital-based studies have found that increased susceptibility to certain infections is associated with low serum levels of mannose-binding lectin (MBL) due to MBL variant alleles. However, the contribution of MBL insufficiency to incidence of common childhood infections at a population level is unknown. OBJECTIVE: To investigate the effect of MBL insufficiency on risk for acute respiratory tract infection (ARI) in unselected children younger than 2 years. DESIGN AND SETTING: Population-based, prospective, cohort study conducted in Sisimiut, Greenland. PARTICIPANTS: Two hundred fifty-two children younger than 2 years who were followed up weekly between August 1996 and August 1998 for morbidity surveillance. MAIN OUTCOME MEASURE: Risk of ARI, based on medical history and clinical examination, compared by MBL genotype, determined from blood samples based on presence of structural and promoter alleles. RESULTS: A 2.08-fold (95% confidence interval [CI], 1.41-3.06) increased relative risk (RR) of ARI was found in MBL-insufficient children (n = 13) compared with MBL-sufficient children (n = 239; P<.001). The risk association was largely restricted to children aged 6 to 17 months (RR, 2.92; 95% CI, 1.78-4.79) while less effect (RR, 1.47; 95% CI, 0.45-4.82) and no effect (RR, 1.00; 95% CI, 0.42-2.37) was shown among children aged 0 to 5 months and 18 to 23 months, respectively. CONCLUSION: These data suggest that genetic factors such as MBL insufficiency play an important role in host defense, particularly during the vulnerable period of childhood from age 6 through 17 months, when the adaptive immune system is immature.

Acute Disease↗
PubMed1997

Endogenous TGF-beta 1 and TGF-beta 2 are not essential for epithelialization and neovascularization in the hairless mouse ear wound model.

BACKGROUND AND AIMS: TGF-beta stimulates neovascularization and epithelialization in healing wounds, yet relatively little is known about the mechanisms involved. Using the hairless mouse ear wound model, we studied the effects endogenous TGF-beta 1 and TGF-beta 2 have on epithelialization and neovascularization following the application of neutralizing antibodies. MATERIAL AND METHODS: Forty-three adult male hairless mice had an excisional wound made on the dorsum of each ear. Using vital microscopy, epithelialization and neovascularization were measured every third day until completion. TGF-beta 1 and TGF-beta 2 antibody, control-IgG, or phosphate buffered saline (PBS) were applied to the wounds. RESULTS AND CONCLUSIONS: Excisional wounds treated with anti-TGF-beta 1 and anti-TGF-beta 2, IgGcontrol IgG, and PBS epithelialized in 11.2 +/- 0.5 days (N = 22), 10.9 +/- 0.6 days (N = 17), and 10.6 +/- 0.6 days (N = 15), respectively and neovascularized in 27.9 +/- 0.5 days (N = 17), 27.1 +/- 0.8 days (N = 14), and 26.1 +/- 0.8 days (N = 10), respectively (mean +/- SEM). There were no significant differences in time to epithelialization and neovascularization between the three groups. Furthermore, there were no differences in the average time course of epithelialization and neovascularization between the three groups throughout the healing process. We conclude that endogenous TGF-beta 1 and TGF-beta 2 are not essential for epithelialization and neovascularization in the hairless mouse ear wound model.

Animals↗
PubMed1982

The chest radiograph in chronic obstructive lung disease compared with measurements of single-breath nitrogen washout and spirometry.

Postero-anterior and lateral chest radiographs were taken in 56 patients with chronic obstructive lung disease in whom the forced expiratory volume (FEV1), total lung capacity (TLC), the residual volume (RV) and the slope of phase III (S3) on the single breath nitrogen washout test (SBN2) were known. The shape and the level of the diaphragm and the shape of the costophrenic sulci, were determined from the chest films and were found to correlate with S3 and FEV1 but not TLC or RV/TLC%.

Adolescent↗