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Biomedical subjects

E Haas

Publications and source records attributed to E Haas.

At least 73 records · Page 4Linked to original sources
PubMed1987

Local structure in a tryptic fragment of performic acid oxidized ribonuclease A corresponding to a proposed polypeptide chain-folding initiation site detected by tyrosine fluorescence lifetime and proton magnetic resonance measurements.

The effects of proline and X-Pro peptide bond conformations on the fluorescence properties of tyrosine in peptides corresponding to parts of a proposed chain-folding initiation site in bovine pancreatic ribonuclease A are examined by time-resolved and steady-state fluorescence spectroscopy. In peptides with Tyr-Pro sequences, the conformational constraints of proline on a preceding residue result in significant fluorescence quenching for both trans and cis peptide bond conformations. Small peptides containing Pro-Tyr sequences, on the other hand, do not exhibit fluorescence quenching compared to Ac-Tyr-NHMe. Studies of fluorescence decay in the tryptic fragment of performic acid oxidized ribonuclease corresponding to residues 105-124 (i.e., O-T-16) demonstrate the presence of at least two environments of the single tyrosine chromophore (in the sequence Asn113-Pro114-Tyr115). In these two (ensemble-averaged) environments, tyrosine has shorter and longer lifetimes, respectively, than in Ac-Tyr-NHMe. The fluorescence heterogeneity in O-T-16 does not correlate with X-Pro cis/trans conformational heterogeneity that can be detected by nuclear magnetic resonance (NMR) spectroscopy. Instead, the fluorescence heterogeneity in O-T-16 arises from the presence of multiple conformations with the same X-Pro peptide bond conformations which interconvert rapidly on the 1H NMR time scale (tau much less than 1 ms) but are distinguishable on the fluorescence lifetime time scale (tau greater than or equal to 1 ns). From comparisons with the tyrosine fluorescence decay of smaller synthetic peptides, it is concluded that the long-lifetime tyrosine fluorescence component of O-T-16 arises from interactions involving residues outside the Asn113-Pro114-Tyr115-Val116-Pro117 sequence, which either stabilize particular local conformations in the vicinity of Tyr115 or act directly to protect Tyr115 from efficient fluorescence quenching. The short-lifetime component of O-T-16 is also observed for the pentapeptide Ac-Asn-Pro-Tyr-Val-Pro-NHMe. The data provide evidence for a nonrandom polypeptide conformation of O-T-16 under conditions of solvent pH and temperature at which the complete disulfide-intact ribonuclease molecule is fully folded. Implications of this work for the interpretation of fluorescence-detected unfolding experiments are discussed.

Amino Acid Sequence↗
PubMed1987

[Status of various surgical technics in nose defects].

The different methods of nasal reconstruction in respect to the number of operative steps, the esthetic and functional result and the risk of complications in the flap are initially examined. Such a review can be of value for the beginner in plastic reconstructive surgery, but it cannot lay down strict recommendations, because variation of the nasal defects with regard to size and site often require an individual technique for closure of the defect.

Humans↗
PubMed1986

Conformational unfolding in the N-terminal region of ribonuclease A detected by nonradiative energy transfer.

Unfolding in the N-terminal region of RNase A was studied by the nonradiative energy-transfer technique. RNase A was labeled with a nonfluorescent acceptor (2,4-dinitrophenyl) on the alpha-amino group and a fluorescent donor (ethylenediamine monoamide of 2-naphthoxyacetic acid) on a carboxyl group in the vicinity of residue 50 (75% at Glu-49 and 25% at Asp-53). The distribution of donor labeling sites does not affect the results of this study since they are close in both the sequence and the three-dimensional structure. The sites of labeling were determined by peptide mapping. The derivatives possessed full enzymatic activity and underwent reversible thermal transitions. However, there were some quantitative differences in the thermodynamic parameters. When the carboxyl groups were masked, there was a 5 degrees C lowering of the melting temperature at pH 2 and 4, and no significant change in delta H(Tm). Labeling of the alpha-amino group had no effect on the melting temperature or delta H(Tm) at pH 2 but did result in a dramatic decrease in delta H(Tm) of the unfolding reaction at pH 4. The melting temperature did not change appreciably at pH 4, indicating that an enthalpy/entropy compensation had occurred. The efficiencies of energy transfer determined with both fluorescence intensity and lifetime measurements were in reasonably good agreement. The transfer efficiency dropped from about 60% under folding conditions to roughly 20% when the derivatives were unfolded with disulfide bonds intact and was further reduced to 5% when the disulfide bonds were reduced. The interprobe separation distance was estimated to be 35 +/- 2 A under folding conditions. The contribution to the interprobe distance resulting from the finite size of the probes was treated by using simple geometric considerations and a rotational isomeric state model of the donor probe linkage. With this model, the estimated average interprobe distance of 36 A is in excellent agreement with the experimental result cited above.

2,4-Dinitrophenol↗
PubMed1986

A series of site-specific fluorescently labeled BPTI derivatives prepared by nonselective acylation and chromatographic separations.

Investigation of conformational transitions and, in particular, the folding/unfolding transitions of globular proteins by means of excitation energy transfer measurements depends on the availability of protein derivatives carrying donor and acceptor probes at well-defined pairs of sites. A series of bovine pancreatic trypsin inhibitor (BPTI) derivatives, each labeled at one of the epsilon-amino groups, was prepared. This was achieved by a nonselective acylation reaction using 7-dimethyl-amino-coumarin-4-acetyl-N-hydroxysuccinimide ester (DACA-NHSIE) as a reagent yielding a mixture of products. The mixture was resolved by affinity chromatography and reversed phase high performance liquid chromatography (HPLC). Four derivatives were obtained, each carrying the probe at one of the four amino groups. Identification of site of labeling and determination of the purity of the products was achieved by HPLC-tryptic peptide mapping. The labeled derivatives are active and can undergo a reversible denaturation/renaturation cycle. The spectral characteristics of the probe make it a suitable acceptor in energy-transfer measurements. The advantage of the approach described here, namely nonselective reaction combined with efficient fractionation procedures for the preparation of site specifically labeled derivatives, is that each of the amino groups can be labeled in a simple procedure, thus allowing for a maximal number of labeling sites which cannot be achieved when site-directed reagents (e.g. specific particular protection) are used. The present method yields derivatives which are useful in energy transfer measurements for determination of intramolecular distances between labeled sites. The derivatives should be useful in the analysis of the mechanism of protein folding and the intermediate structures involved.

Acylation↗
PubMed1986

Reminiscences and reflections.

Some of Dr. Goldblatt's important contributions during a notable research career of more than 50 years are reviewed. The research on rickets (1922-1932), culminating in the discovery of the antirachitic effect of sterol irradiated with ultraviolet light. The research on cancer (1930-1974), demonstrating the malignant transformation of normal fibroblasts caused by hypoxia and prevented by increased availability of oxygen. The production of benign and chronic experimental hypertension by renal ischaemia (1934-1976). The large-scale isolation of human and animal renin (1943-1976). The production of antirenin by immunization with heterologous or chemical only modified homologous renin. Antirenin successfully reversed both acute and chronic experimental renal hypertension, thereby demonstrating the primary role of the renin-angiotensin system in maintaining the elevated blood pressure and that this type of hypertension is reversible even in the chronic phase of 6 years.

Animals↗
PubMed1984

Intramolecular dynamics of chain molecules monitored by fluctuations in efficiency of excitation energy transfer. A theoretical study.

The fluorescence quantum yield of a polymer molecule to which an energy donor chromophore and an energy acceptor chromophore are attached depends on the distance between the donor and acceptor chromophores. If this distance fluctuates with time, the fluorescence intensity is expected to fluctuate as well, and the time course of the intensity fluctuations will be correlated with the time course of the changes in the interchromophore distance. The intensity fluctuations are experimentally measurable if the number of illuminated molecules is small. A theoretical treatment of such fluorescence intensity fluctuations is presented in terms of a parameter that describes the polymer chain dynamics. Computer simulations were performed to illustrate the dependence of the autocorrelation function of the intensity fluctuations on the polymer chain conformation, the interchromophore energy transfer properties, and the macromolecular dynamics. These simulations demonstrate that the intensity fluctuations due to nonradiative energy transfer between chromophores attached to polymer chains can be large enough to be experimentally useful in the study of intramolecular dynamics of macromolecules.

Biopolymers↗
PubMed1984

Angiotensin-producing enzyme I of serum: formation by immunization with renin.

Immunization with renin from the kidneys of hog, beef, dog, rabbit and man induced the formation of a highly active enzyme (enzyme I) in the serum of dogs, guinea pigs, rabbits and rats. Enzyme I produces angiotensin I maximally at pH 4.7, up to 2900 ng/ml serum/h, i.e. at a rate 2500 times higher than the endogenous renin of normal serum. At pH 7.2 the angiotensin I production by enzyme I is about 16 to 28 times higher than that of plasma renin. Enzyme I is produced by immunization with renin and not by other kidney proteins. Enzymatically-active renin is required and separate mechanisms are involved in the formation of enzyme I and antirenin. Enzyme I is not identical to renin, pepsin, cathepsin D, plasmin, tonin or cathepsin G and it is inhibited by pepstatin, but not by diisopropyl fluorophosphate.

Animals↗
PubMed1983

[Tubed pedicle flap in the head-neck area from a current viewpoint].

After a review of the biological fundamentals of tubed pedicle flap plasty by advantages and disadvantages as well as the techniques of formation of flaps, transplantation of flaps and migration of flaps are discussed. Furthermore the pedicle flap of fat is presented. Today the skin flaps of the postero-lateral cervical region are of great practical importance due to the fact that they are commonly used both for reconstructive surgery of face burns and of the auricle, and for closure of tumor defects in the oral cavity. In the age of microvascular surgery and the formation of myocutaneous flaps the flap has kept its definite indication, especially for the repair of greater defects of the face, oral cavity and congenital facial hemiatrophy. The repair consists of the replacement of missing subcutaneous fat.

Burns↗
PubMed1982

[Oncological principles of the treatment of facial skin cancer].

The complete mastery of reconstructive plastic surgery is a basic requirement essential for sufficient radical treatment of basal cell carcinoma in the facial area. Furthermore, the subclinical growth of the basal cell carcinoma must be taken into consideration. One can assume that the growth of the b.c.c. is much greater than the apparent clinical limits, especially in cases of recurrent tumours, tumours of long standing, tumours in frontal and temporal regions, as well as tumours with diameters of more than 2 cm and scleroderma growth. In such cases a safety margin of 8-15 mm is required, whereas in primary and locally well-defined b.c.c. a safety margin of 3-5 mm is regarded as sufficient. Following the examination of the microscopically controlled surgery developed by Mohs, which is suitable for improvement of the five-year cure rate after surgical treatment of b.c.c., the treatment of the squamous cell carcinoma of the bottom lip is dealt with. Taking into account the tendency of these tumours to metastasize, it is advised to carry out an elective neck-dissection confined to the suprahyoidal region in case of large squamous cell carcinoma and also in suspicious metastatic changes in the lymph nodes. The diagnosis of a malignant melanoma is fundamentally histological: The tumour is electrically excised with a clearance safety margin of surrounding skin of 0.5-1 cm if clinically there appears to be a 10% likelihood of the tumour being a malignant melanoma. If the histological frozen section of the excised tumour confirms the suspected diagnosis, in cases of high-risk melanomas an area of not less than 3 cm from the edge of the primary tumour must be reexcised. A free skin graft is preferred to cover the defect rather than a plastic repair by a pedicle-flap graft. The elective lymph node dissection in the case of malignant melanoma stage I is made dependent on the level of invasion and on the thickness of the tumour. Low-risk melanomas are operated on locally only whereas an elective dissection of the regional lymph nodes is generally recommended in cases of high-risk melanomas.

Basal Cell Carcinoma↗
PubMed1980

Human renal renin. Complete purification and characterization.

Complete purification of human renin from noncancerous, autopsied kidneys is reported. A 480,000-fold purification was achieved to yield renin with a specific activity of 950 Goldblatt units/mg. This preparation satisfied multiple criteria of purity as tested by polyacrylamide gel electrophoresis, isoelectric focusing, specific activity, analytical ultracentrifugation, and immunodouble diffusion. The molecular weight of the pure enzyme determined by sedimentation equilibrium is 40,000. The apparent molecular weight estimated by gel filtration is 41,000. The enzyme has an isoelectric point of pH 5.7. Human renin shows an affinity for concanavalin A, suggesting the presence of carbohydrates. These properties and the amino acid composition of human renin are different from those of renin obtained from other mammalian species. Human renin antibodies prepared with the pure enzyme preparation showed negligible cross-reactivity with renin from other mammalian species. The activity with homologous human renin substrate has a pH optimum of 6, whereas with substrates from other mammalian species the optima were in higher or lower pH ranges.

Amino Acids↗
PubMed1980

Bioluminescence from single bacterial cells exhibits no oscillation.

Since the usual measurements of light emission from marine bacteria involve many (10(6)-10(10)) cells, the question has often been raised as to whether or not the individual cell's luminescence is truly continuous. To investigate this question, we assembled a sensitive photo-counting system with computerized data acquisition. Several luminous species were studied: Beneckea harveyi, Photobacterium belozerskii, P. fischeri, and P. leiognathi. Isolated single cells gave count rates ranging from 2 to 10 times the background, depending on the brightness of the strain and the state of induction. No flashes, bursts, or oscillations were evident from data collected in counting intervals of 100 ms, using both photo time-correction and power spectral analysis. Our algorithms could detect an oscillating component with an intensity as low as 0.3% of the average, as determined by the analysis of reference light sources. That photons are emitted randomly was further shown by the fact that the count distribution from the living cell closely matched that of a reference light source attenuated to the same average count rate.

Kinetics↗
PubMed1980

[Special flap-techniques in the treatment of nasal defects (author's transl)].

The median frontal flap described by Kazanjian, a horizontal or slightly oblique frontal flap and the scalp flap described by Converse are discussed. It is shown that each method can be used for specific indications. The choice of method by the less experienced is therefore facilitated. A. The median frontal flap is especially indicated for the grosser defects of the back and the lateral parts of the nose. B. The horizontal or slightly oblique frontal flap is especially indicated for subtotal or total defects of the nasal alae or tip of the older patient, who can not undergo repeated surgery or prolonged hospitalisation. C. The frontal scalp flap is especially indicated for the grosser subtotal or total defects of the external nose. - The fronto-temporal flap, described by Schmid, and the "Island-flap" belong to flaps, who need more experience on the field of plastic surgery. The latter is described in his different variations and it is shown the advantage of "one time" equalization of defects by using this technique. The "bilobed flap" too allowes the "one time" equalization and is suitable for the surgery of defects in the region of the tip of the nose.

Humans↗