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Biomedical subjects

S Völker

Publications and source records attributed to S Völker.

11 recordsLinked to original sources
PubMed2005

Green and red fluorescent proteins: photo- and thermally induced dynamics probed by site-selective spectroscopy and hole burning.

The cloning and expression of autofluorescent proteins in living matter, combined with modern imaging techniques, have thoroughly changed the world of bioscience. In particular, such proteins are widely used as genetically encoded labels to track the movement of proteins as reporters of cellular signals and to study protein-protein interactions by fluorescence resonance energy transfer (FRET). Their optical properties, however, are complex and it is important to understand these for the correct interpretation of imaging data and for the design of new fluorescent mutants. In this Minireview we start with a short survey of the field and then focus on the photo- and thermally induced dynamics of green and red fluorescent proteins. In particular, we show how fluorescence line narrowing and high-resolution spectral hole burning at low temperatures can be used to unravel the photophysics and photochemistry and shed light on the intricate electronic structure of these proteins.

Biophysics↗
PubMed2000

Photophysics and optical switching in green fluorescent protein mutants.

We demonstrate by using low-temperature high-resolution spectroscopy that red-shifted mutants of green fluorescent protein are photo-interconverted among three conformations and are, therefore, not photostable "one-color" systems as previously believed. From our experiments we have further derived the energy-level schemes governing the interconversion among the three forms. These results have significant implications for the molecular and cell biological applications of the green fluorescent protein family; for example, in fluorescence resonant energy transfer experiments, a change in "color" on irradiation may not necessarily be due to energy transfer but can also arise from a photo-induced conversion between conformers of the excited species.

Green Fluorescent Proteins↗
PubMed1999

Three photoconvertible forms of green fluorescent protein identified by spectral hole-burning.

Several studies have led to the conclusion that, in the green fluorescent protein (GFP) of the jellyfish Aequorea victoria, a photoconversion involving excited-state proton transfer occurs from an A- to a B-form, while an intermediate I-form was held responsible for the green fluorescence. Here we have identified the I-form of wild-type GFP in absorption, located the 0-0 transitions of all three forms A, B and I, and determined vibrational frequencies of the ground and excited states. The intrinsically narrow 0-0 transitions are revealed by the wavelengths at which holes can be burnt. The pathways of photointerconversion are unraveled by excitation, emission and hole-burning spectroscopy. We present an energy-level scheme that has significant implications for GFP-mutants, which likewise can occur in the three photo-interconvertible forms.

Absorption↗
PubMed1998

Relationships between infant crying, birth complications, and maternal variables.

The aim of the study is to identify factors influencing infants' crying behaviour (total crying duration, length of crying bouts, and frequency of crying). The searching for variables explaining inter-individual differences requires a sufficient stability of the cry parameters at least over short time intervals. Thus, a second aim is to assess the intra-individual stability of the crying behaviour in an age range from 3 to 12 months. Sixty-two mother-child dyads participated in the study. The results show substantial stabilities of the crying behaviour of infants between 3 and 12 months of age. This is related to the amount of crying as well as to the pattern of crying shown by the children over a 24 h interval. The typical cry pattern is characterized by peaks at 12.00 h and early in the evening, although there are large individual differences between the children with regard to cry durations at each hour of the day. Regarding the cry durations at 3 months of age, birth complications and the perceived emotional atmosphere in the mothers' family of origin are the major contributing factors.

Adult↗
PubMed1997

Intuitive parenting and infant behavior: concepts, implications, and empirical validation.

On the basis of the concept of intuitive parenting, the expectation was formulated that a mother's tendency to reflect on her parenting behavior would impede intuitive responses to infant signals. Also, a high quality of parental interactional behavior was expected to be related to fewer problems of the child (e.g., less crying, fewer reported difficulties, fewer health problems). An observational study with 62 mothers and their 3-month-old children confirmed the assumption that reflection about parenting during face-to-face interactions interferes with intuitive behavior. However, in contrast to initial expectations, a high quality of parenting was related, not to fewer, but rather to more health and behavioral problems of the child. Conceptual differentiations of the initial assumptions are discussed.

Adult↗
PubMed1989

[Arteriosclerotic changes of the brain and heart in relation to cardiac decompensation and arrhythmia in patients with cerebrovascular insufficiency].

In 150 patients with an acute cerebrovascular insufficiency we asked the following questions: 1. How often appear together the cardiac decompensation and disturbances of cardiac rhythm, 2. symptoms of hypertrophy and disturbances of cardiac rhythm and 3. arteriosclerosis of the cerebral and coronary vessels in deceased patients. The number of patients examined showed 26.7% of patients in whom a combination of symptoms of cardiac decompensation and disturbances of cardiac rhythm was present. The combination of signs of hypertrophy in the electrocardiogram and disturbances of cardiac rhythm was registered 39 times (26.0%). The arteriosclerosis was found in 68.2% of the patients in post-mortem examination. There was a high correlation between the sclerosis of the intracranial cerebral brains (65.9%) and the sclerosis of the coronary vessels (75.0%). It is referred to the possibilities of the prevention of the cerebrovascular insufficiency and the early therapy of hypertony, the cardiac decompensation and disturbances of cardiac rhythm.

Aged↗
PubMedDate not supplied

[Hypertension and heart failure in patients with cerebrovascular insufficiency].

Concerning 150 patients suffering from acute cerebrovascular insufficiency we asked the following questions: 1. How often did cardiac decompensation occur, 2. How often did hypertension and hypertrophic symptoms occur in the electrocardiogram, and 3. How often did arteriosclerosis of the cerebral and coronary vessels occur together in deceased patients? Among the patients examined were 47.3% who showed symptoms of cardiac decompensation. Hypertension was found in 60.7% of the patients. The combination of symptoms of hypertrophy in the electrocardiogram and cardiac dysrhythmia was registered 39 times (26.0%). Arteriosclerosis was found in 68.2% of the post-mortem examinations. A high correlation was found between the sclerosis of the intracranial cerebral vessels (65.9%) and the sclerosis of the coronaries (75.0%). The possibilities of the prevention and deceleration, resp., of cerebrovascular insufficiency by early therapy of hypertension and of cardiac decompensation are pointed out.

Aged↗