Über die durch Trocknen bewirkten Absorptions-Änderungen von Chloroplasten und Algen

1965 ◽  
Vol 20 (5) ◽  
pp. 482-487 ◽  
Author(s):  
Wilhelm Menke ◽  
C. Stacey French ◽  
Warren L. Butler
Keyword(s):  
Light Scattering ◽  
Absorption Band ◽  
Chlorophyll A ◽  
Freeze Drying ◽  
X Ray ◽  
Derivative Spectra ◽  
Freeze Dried ◽  
Two Factors ◽  
Isolated Chloroplasts

Derivative spectra of isolated chloroplasts in water of air dried and freeze dried chloroplasts are compared with spectra of lipid extracts free of solvent. During freeze drying the chlorophyll does not dissolve in the separated chloroplast lipids as appears to follow from X-ray investigations.By freeze drying, the red absorption of algae and isolated chloroplasts is shifted more or less to longer wavelengths. During slow drying in air the red absorption band is shifted by some algae to shorter wavelengths. Some algae do not show this shift. These changes of absorption are partly caused by different selective light scattering and partly by an alteration of the relative amounts of various spectroscopic forms of the chlorophyll a. A clear decision upon these two factors is impossible.

Revealing gross three-dimensional structure in the SEM

1987 ◽  
Vol 45 ◽  
pp. 656-657
Author(s):  
Sterling P. Newberry
Keyword(s):  
Freeze Drying ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Small Object ◽  
Final Solution ◽  
Dimensional Representation ◽  
X Ray ◽  
Three Dimensional Representation ◽  
Freeze Dried ◽  
Critical Point Drying

The beautiful three dimensional representation of small object surfaces by the SEM leads one to search for ways to open up the sample and look inside. Could this be the answer to a better microscopy for gross biological 3-D structure? We know from X-Ray microscope images that Freeze Drying and Critical Point Drying give promise of adequately preserving gross structure. Can we slice such preparations open for SEM inspection? In general these preparations crush more readily than they slice. Russell and Dagihlian got around the problem by “deembedding” a section before imaging. This some what defeats the advantages of direct dry preparation, thus we are reluctant to accept it as the final solution to our problem. Alternatively, consider fig 1 wherein a freeze dried onion root has a window cut in its surface by a micromanipulator during observation in the SEM.

Synthesis of Porous Ceramics Through Directional Solidification and Freeze-Drying

2003 ◽  
Vol 788 ◽  
Author(s):  
Predrag Kisa ◽  
Patrick Fisher ◽  
Al Olszewski ◽  
Ian Nettleship ◽  
Nicholas G. Eror
Keyword(s):  
Freeze Drying ◽  
Three Dimensional ◽  
Porous Ceramics ◽  
Porous Structures ◽  
Directionally Solidified ◽  
X Ray Diffraction ◽  
Microstructural Characteristics ◽  
X Ray ◽  
Freeze Dried ◽  
Silica Sols

ABSTRACTThis study investigated the microstructural characteristics of directionally solidified freeze-dried silica sols. Porous structures were formed by depositing silica sol on silicon (100) single crystals. The deposited sols were unidirectionaly solidified by placing the silicon substrate on a copper block immersed in liquid nitrogen and then subsequently freeze-dried. Freeze drying removal of ice crystals created three-dimensional pore channels ranging from 3 to10 micrometers in diameter aggregated in grain like colonies 50–100 micrometers in diameter. Pore size, spacing, colony size and microstructure were determined using optical microscopy (OM) and scanning electron microscopy (SEM) while the structure of the amorphous SiO2 was characterized by X-ray diffraction (XRD). The microstructure results are compared and contrasted with silica aerogel obtained through conventional processing using supercritical CO2.

scholarly journals Minimizing experimental artefacts in synchrotron-based X-ray analyses of Fe speciation in tissues of rice plants

2019 ◽  
Vol 26 (4) ◽  
pp. 1272-1279 ◽  
Author(s):  
Peng Wang ◽  
Brigid A. McKenna ◽  
Neal W. Menzies ◽  
Cui Li ◽  
Chris J. Glover ◽  
...  
Keyword(s):  
Freeze Drying ◽  
Plant Root ◽  
Experimental Conditions ◽  
X Ray ◽  
Freeze Dried ◽  
Fe Speciation ◽  
Root Tissues ◽  
X Ray Absorption ◽  
Beam Damage

Iron (Fe) plays an important role within environmental systems. Synchrotron-based X-ray approaches, including X-ray absorption spectroscopy (XAS), provide powerful tools for in situ analyses of Fe speciation, but beam damage during analysis may alter Fe speciation during its measurement. XAS was used to examine whether experimental conditions affect the analysis of Fe speciation in plant tissues. Even when analyzed in a cryostat at 12 K, it was found that FeIII can rapidly (within 0.5–1 min) photoreduce to FeII, although the magnitude of photoreduction varied depending upon the hydration of the sample, the coordination chemistry of the Fe, as well as other properties. For example, photoreduction of FeIII was considerably higher for aqueous standard compounds than for hydrated plant-root tissues. The use of freeze-dried samples in the cryostat (12 K) markedly reduced the magnitude of this FeIII photoreduction, and there was no evidence that the freeze-drying process itself resulted in experimental artefacts under the current experimental conditions, such as through the oxidation of FeII, although some comparatively small differences were observed when comparing spectra of hydrated and freeze-dried FeII compounds. The results of this study have demonstrated that FeIII photoreduction can occur during X-ray analysis, and provides suitable conditions to preserve Fe speciation to minimize the extent of beam damage when analyzing environmental samples. All studies utilizing XAS are encouraged to include a preliminary experiment to determine if beam damage is occurring, and, where appropriate, to take the necessary steps (such as freeze drying) to overcome these issues.

Preparation and characterization of dried cellulose nanofibrils

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jianping Ni ◽  
Chen Gong ◽  
Zhenghua Su ◽  
Chao Tian
Keyword(s):  
Spray Drying ◽  
Freeze Drying ◽  
Cellulose Nanofibrils ◽  
Time Dependent ◽  
X Ray ◽  
Original State ◽  
Final Mass ◽  
Freeze Dried ◽  
Spray Dried

Abstract One of the main manufacturing challenges is to obtain dried cellulose nanofibrils (CNFs) so that they can be cost effectively transported to customers. This work presents a study on using two methods of drying: freeze drying and spray drying; these dried CNFs were then characterized. The dried CNFs from either freeze drying or spray drying could not recover their original state after simple re-dispersion in water. Compared to spray dried CNFs, the microstructure of the freeze dried CNFs remained in a better shape. This was because the packing of nanofibrils as a result of freeze drying was not as tight as that from spray drying. It was demonstrated by the lower final mass residue and crystallinity of the freeze-dried CNFs, which led to better re-dispersion in water. X-ray diffractometry proved the occurrence of aggregation/hornification of the dried CNFs with increased crystallinity. Time-dependent sedimentation confirmed that the dried CNFs were incapable of forming stable water-re-dispersible suspensions.

Effect of the degree of neutralization on the micellization of block ionomers

1995 ◽  
Vol 73 (11) ◽  
pp. 2086-2093 ◽  
Author(s):  
Karine Khougaz ◽  
Diep Nguyen ◽  
Adi Eisenberg ◽  
Claudine E. Williams
Keyword(s):  
Light Scattering ◽  
Block Copolymers ◽  
Small Angle ◽  
Dynamic Equilibrium ◽  
Scattered Light ◽  
Single Chain ◽  
X Ray ◽  
X Ray Scattering ◽  
Freeze Dried ◽  
Ray Scattering

The effect of neutralization on the micellization of polystyrene-b-poly(acrylic acid) (PS-b-PAA) was investigated by static light scattering (SLS) and small-angle X-ray scattering (SAXS). The block copolymers, present initially in single chain form in either dioxane or benzene–methanol (90/10 (v/v)), were neutralized to different degrees by the addition of cesium hydroxide dissolved in methanol. The solutions were simultaneously monitored by SLS. It was found that micelle formation began near 5% neutralization. The normalized scattered light intensity at 90° (I90/c) increased dramatically in the neutralization range between ca. 10 and 60%. For neutralization degrees between 60 and ca. 100%, I90/c did not change significantly with a further increase in the percent of neutralization. In the second part of the study, two block copolymers, PS(600)-b-PAA(34) and PS(600)-b-PAA(45) (the number of monomer units is given in parentheses), were prepared from benzene–methanol (90/10 (v/v)) with different degrees of neutralization: 5, 25, 60, 100, and 150%. The resulting solutions were freeze-dried and the dried samples were redissolved in toluene. These samples were investigated by SLS and SAXS. By SLS, the aggregation numbers (f) were found to be the same between 5 and 60% neutralization. An increase in f was observed in going from 60 to 100%; i.e., f increased from 82 to 92 for PS(600)-b-PAA(34), and from 79 to 110 for PS(600)-b-PAA(45). The f values for the two block copolymers at 150% neutralization were found to be the same as those for 100% neutralization. The core radii values (Rcore) were measured for the neutralized PS(600)-b-PAA(45) samples at 0.05 g/mL in toluene by SAXS. The Rcore values increased from 5 to 60% neutralization, remained constant from 60 to 100%, and increased again in the range from 100 to 150%. The results are explained by dynamic considerations. For low percent neutralization, between 5 and 60%, the micelles and single chains are proposed to be in a dynamic equilibrium state. For higher percent neutralization, between 60 and 100%, the dynamics are probably much slower. Keywords: block copolymers, micelles, ionomers, light scattering, small angle X-ray scattering (or SAXS).

scholarly journals Development of Intranasal Levothyroxine Powder Delivery for Hypothyroidism

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A828-A829
Author(s):  
Syed Ali Imran ◽  
Obinna Esomchukwu ◽  
Remigius Agu
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Surface Morphology ◽  
Freeze Drying ◽  
Significant Proportion ◽  
In Vitro Release ◽  
X Ray ◽  
Freeze Dried ◽  
Vitro Release

Abstract Background: Hypothyroidism affects 3-5% of the general population with oral levothyroxine (LT4) being the predominant replacement therapy. However, significant proportion of hypothyroid patients are unable to absorb oral replacement leading to therapeutic failure and may require injectable thyroxine. Objectives: To develop non-invasive, less costly, and patient-friendly LT4 nasal delivery alternative using mucoadhesive polymers: chitosan and hydroxypropylmethylcellulose (HPMC). Methods: Six nasal LT4 formulations were developed with either chitosan or hydroxypropyl methylcellulose as mucoadhesive. The formulations were prepared through freeze-drying by varying the drug to polymer ratio (1:1, 1:3, and 1:5). The percentage drug yield was calculated by analyzing the weight of the formulation pre- and post-freeze drying. HPLC analysis was conducted to determine the amount of LT4 loaded in each formulation. Furthermore, the surface morphology, particle size, zeta potential, differential scanning calorimetry, X-ray diffraction as well as the in vitro release were assessed to determine the physicochemical properties and release characteristics of the formulations, respectively. Results: Both percentage drug loading and yield were > 70% for all the formulations. The freeze-dried formulations displayed a compact needle-like surface morphology. LT4-chitosan formulations, 1:1, 1:3, and 1:5 had mean particle size of 2.45 ± 0.88 µm, 2.76 ± 1.38 µm, and 1.59 ± 0.27 µm, respectively. Mean particle sizes for 1:1, 1:3, and 1:5 LT4-HPMC formulations were 0.56 ± 0.02 µm, 0.22 ± 0.06 µm, and 0.46 ± 0.04 µm. Zeta potential for LT4-chitosan formulation 1:1, 1:3, and 1:5 were -18.7 ± 1.00 mV, -16.2 ± 0.79 mV, and -19.17 ± 1.01 mV, respectively. LT4-HPMC 1:1, 1:3, and 1:5 formulations had zeta charges of -11.66 ± 3.16 mV, -6.06 ± 3.92 mV, and -9.53 ± 1.68 mV, respectively. Differential calorimetric analysis confirmed drug-polymer integration in all formulations, and X-ray powder diffraction showed both chitosan and HPMC formulations as crystalline configuration. The formulations with the highest in vitro release were LT4-HPMC 1:3 and LT4-chitosan 1:5. Conclusions: Results of this study suggest that both chitosan and HPMC can be used as sustained release polymers for the intranasal delivery of LT4.

Stability of freeze-dried products subjected to microcomputed tomography radiation doses

2021 ◽  
Vol 73 (2) ◽  
pp. 212-220
Author(s):  
Tim Wenzel ◽  
Achim Sack ◽  
Patrick Müller ◽  
Thorsten Poeschel ◽  
Sonja Schuldt-Lieb ◽  
...  
Keyword(s):  
Freeze Drying ◽  
Structural Information ◽  
Microcomputed Tomography ◽  
Radiation Doses ◽  
Stability Testing ◽  
X Ray ◽  
Accelerated Stability ◽  
Freeze Dried ◽  
The Stability ◽  
Non Destructive

Abstract Objectives Microcomputed tomography (µCT) is a powerful analytical tool for non-invasive structural analysis. The stability of drug substances and formulations subjected to X-ray radiation may be a concern in the industry. This study examines the effect of X-ray radiation on the stability of freeze-dried pharmaceuticals. The investigation is a proof of concept study for the safety of µCT X-ray radiation doses during the non-destructive investigation of freeze-dried products. Methods Different formulations of clotrimazole, insulin and l-lactate dehydrogenase were freeze-dried and the products exposed to a defined dose of radiation by µCT. Conservative freeze-drying conditions were used. Irradiated and normal samples were analysed for their stability directly after freeze-drying and after stability testing. Key findings The stability of model compounds was well maintained during freeze-drying. Some degradation of all compounds occurred during accelerated stability testing. The results showed no differences between the irradiated and normal state directly after freeze-drying and accelerated stability testing. Conclusions No evidence of a detrimental effect of 100 Gy X-ray exposure on a model small molecule, peptide and protein compound was found while useful structural information could be obtained. Consequently, the technology may be useful as a non-destructive tool for product inspections if the formulation proves stable.

scholarly journals Ultrastructure and energy-dispersive x-ray microanalysis of cartilage after rapid freezing, low temperature freeze drying, and embedding in Spurr's resin.

1985 ◽  
Vol 33 (10) ◽  
pp. 1073-1079 ◽  
Author(s):  
J Appleton ◽  
R Lyon ◽  
K J Swindin ◽  
J Chesters
Keyword(s):  
Low Temperature ◽  
Freeze Drying ◽  
Energy Dispersive ◽  
Freezing Process ◽  
Rapid Freezing ◽  
Thin Sections ◽  
X Ray ◽  
Freeze Dried ◽  
Rapid Production ◽  
Ideal Method

In order to undertake meaningful high-resolution x-ray microanalysis of tissues, methods should be used that minimize the introduction of artefacts produced by loss or translocation of ions. The most ideal method is rapid freezing but the subsequent sectioning of frozen tissues is technically difficult. An alternative method is to freeze dry the tissues at a low temperature, and then embed them in resin. This facilitates the rapid production of reproducible thin sections. With freeze-dried, embedded hypertrophic cartilage, the morphology was similar to that seen using aqueous fixatives even when no additional electron density is introduced by the use of osmium vapor. Energy-dispersive analysis of specific areas show that little or no loss or migration of ions occurs from structures such as mitochondria. Mitochondrial granules consisting of calcium and phosphorus precipitates were not observed except where the cells were damaged as a result of the freezing process. This may suggest that these granules only appear when tissue is damaged because of inadequate preservation.

Scanning Electron Microscopy-cuticular Lesions on the Roundworm Ascaris Suum

1970 ◽  
Vol 28 ◽  
pp. 114-115
Author(s):  
P. A. Madden ◽  
W. R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Freeze Drying ◽  
Room Temperature ◽  
Secondary Electron ◽  
Distilled Water ◽  
Freeze Dried ◽  
Silver Paint ◽  
To Come ◽  
Scanning Electron

The intestinal roundworm of swine is pinkish in color and about the diameter of a lead pencil. Adult worms, taken from parasitized swine, frequently were observed with macroscopic lesions on their cuticule. Those possessing such lesions were rinsed in distilled water, and cylindrical segments of the affected areas were removed. Some of the segments were fixed in buffered formalin before freeze-drying; others were freeze-dried immediately. Initially, specimens were quenched in liquid freon followed by immersion in liquid nitrogen. They were then placed in ampuoles in a freezer at −45C and sublimated by vacuum until dry. After the specimens appeared dry, the freezer was allowed to come to room temperature slowly while the vacuum was maintained. The dried specimens were attached to metal pegs with conductive silver paint and placed in a vacuum evaporator on a rotating tilting stage. They were then coated by evaporating an alloy of 20% palladium and 80% gold to a thickness of approximately 300 A°. The specimens were examined by secondary electron emmission in a scanning electron microscope.

Artefacts in the x-ray microanalysis of frozen-hydrated biological samples

1987 ◽  
Vol 45 ◽  
pp. 658-659
Author(s):  
Patrick Echlin
Keyword(s):  
Electron Scattering ◽  
Biological Samples ◽  
Fracture Face ◽  
Detailed Structure ◽  
X Ray ◽  
Morphological Appearance ◽  
The Poor ◽  
Freeze Dried

A number of papers have appeared recently which purport to have carried out x-ray microanalysis on fully frozen hydrated samples. It is important to establish reliable criteria to be certain that a sample is in a fully hydrated state. The morphological appearance of the sample is an obvious parameter because fully hydrated samples lack the detailed structure seen in their freeze dried counterparts. The electron scattering by ice within a frozen-hydrated section and from the surface of a frozen-hydrated fracture face obscures cellular detail. (Fig. 1G and 1H.) However, the morphological appearance alone can be quite deceptive for as Figures 1E and 1F show, parts of frozen-dried samples may also have the poor morphology normally associated with fully hydrated samples. It is only when one examines the x-ray spectra that an assurance can be given that the sample is fully hydrated.

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